2.2.0.25falsefalse006080 - Disclosure - FAIR VALUE MEASUREMENTStruefalsefalse1falsefalseUSDfalsefalse1/1/2010 - 12/31/2010 USD ($) USD ($) / shares $c00032http://www.sec.gov/CIK0000072020duration2010-01-01T00:00:002010-12-31T00:00:00u000Standardhttp://www.xbrl.org/2003/iso4217USDiso42170u001Standardhttp://www.xbrl.org/2003/instancesharesxbrli0u002Dividehttp://www.xbrl.org/2003/iso4217USDiso4217http://www.xbrl.org/2003/instancesharesxbrli0USDUSD$2true0gas_NotesToFinancialStatementsAbstractgasfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringNo definition available.falsefalseNotes to Financial Statements [Abstract]3false0us-gaap_FairValueMeasurementInputsDisclosureTextBlockus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div style="LINE-HEIGHT: 1.5"><table style="FONT-SIZE: 10pt; FONT-FAMILY: times new roman" cellspacing="0" cellpadding="0" width="100%" align="center" border="0"><tr valign="top"><td style="WIDTH: 18pt; LINE-HEIGHT: 1.5"><div style="MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5; MARGIN-RIGHT: 0pt">7.</div></td><td style="LINE-HEIGHT: 1.5"><div style="LINE-HEIGHT: 1.5" align="left">FAIR VALUE MEASUREMENTS</div></td></tr></table></div><div style="DISPLAY: block; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5"> </div><div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5; MARGIN-RIGHT: 0pt" align="left">The fair value of assets and liabilities that are measured on a recurring basis are categorized in the table below (in millions) into three broad levels (with Level 1 considered the most reliable) based upon the valuation inputs.</div><div style="DISPLAY: block; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5"> </div><div style="LINE-HEIGHT: 1.5" align="center"><table style="FONT-SIZE: 10pt; FONT-FAMILY: times new roman" cellspacing="0" cellpadding="0" width="100%"><tr><td valign="bottom" width="15%">  </td><td style="LINE-HEIGHT: 1.5" valign="bottom" width="2%"> </td><td style="LINE-HEIGHT: 1.5" valign="bottom" width="7%" colspan="2"><div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5; MARGIN-RIGHT: 0pt" align="center">Quoted prices in active markets</div></td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="LINE-HEIGHT: 1.5" valign="bottom" width="2%"> </td><td style="LINE-HEIGHT: 1.5" valign="bottom" width="7%" colspan="2"><div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5; MARGIN-RIGHT: 0pt" align="center">Significant observable inputs</div></td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="LINE-HEIGHT: 1.5" valign="bottom" width="2%"> </td><td style="LINE-HEIGHT: 1.5" valign="bottom" width="7%" colspan="2"><div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5; MARGIN-RIGHT: 0pt" align="center">Significant unobservable inputs</div></td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="LINE-HEIGHT: 1.5" valign="bottom" width="2%"> </td><td style="LINE-HEIGHT: 1.5" valign="bottom" width="7%" colspan="2"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td></tr><tr><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5" valign="bottom" width="15%">  </td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5" valign="bottom" width="2%"> </td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 2px solid" valign="bottom" width="7%" colspan="2"><div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5; MARGIN-RIGHT: 0pt" align="center">(Level 1)</div></td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5" valign="bottom" width="2%"> </td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 2px solid" valign="bottom" width="7%" colspan="2"><div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5; MARGIN-RIGHT: 0pt" align="center">(Level 2)</div></td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5" valign="bottom" width="2%"> </td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 2px solid" valign="bottom" width="7%" colspan="2"><div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5; MARGIN-RIGHT: 0pt" align="center">(Level 3)</div></td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5" valign="bottom" width="2%"> </td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 2px solid" valign="bottom" width="7%" colspan="2"><div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5; MARGIN-RIGHT: 0pt" align="center">Total</div></td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td></tr><tr><td style="LINE-HEIGHT: 1.5" valign="bottom" align="left" width="15%"><div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5; MARGIN-RIGHT: 0pt" align="left">December 31, 2010</div></td><td style="LINE-HEIGHT: 1.5" valign="bottom" width="2%"> </td><td style="LINE-HEIGHT: 1.5" valign="bottom" width="7%" colspan="2"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="LINE-HEIGHT: 1.5" valign="bottom" width="2%"> </td><td style="LINE-HEIGHT: 1.5" valign="bottom" width="7%" colspan="2"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="LINE-HEIGHT: 1.5" valign="bottom" width="2%"> </td><td style="LINE-HEIGHT: 1.5" valign="bottom" width="7%" colspan="2"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="LINE-HEIGHT: 1.5" valign="bottom" width="2%"> </td><td style="LINE-HEIGHT: 1.5" valign="bottom" width="7%" colspan="2"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td></tr><tr bgcolor="#e2eef5"><td style="LINE-HEIGHT: 1.5" valign="bottom" align="left" width="15%"><div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5; MARGIN-RIGHT: 0pt" align="left">Assets</div></td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5" valign="bottom" width="2%"> </td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5" valign="bottom" width="7%" colspan="2"> </td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5" valign="bottom" width="2%"> </td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5" valign="bottom" width="7%" colspan="2"> </td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5" valign="bottom" width="2%"> </td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5" valign="bottom" width="7%" colspan="2"> </td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5" valign="bottom" width="2%"> </td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5" valign="bottom" width="7%" colspan="2"> </td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td></tr><tr bgcolor="white"><td style="LINE-HEIGHT: 1.5" valign="bottom" align="left" width="15%"><div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5; MARGIN-RIGHT: 0pt" align="left">   Money market funds</div></td><td style="LINE-HEIGHT: 1.5" valign="bottom" align="left" width="2%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" width="3%">$</td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: right" valign="bottom" width="4%">82.9</td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="LINE-HEIGHT: 1.5" valign="bottom" align="left" width="2%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" width="3%">$</td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: right" valign="bottom" width="4%">-</td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="LINE-HEIGHT: 1.5" valign="bottom" align="left" width="2%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" width="3%">$</td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: right" valign="bottom" width="4%">-</td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="LINE-HEIGHT: 1.5" valign="bottom" align="left" width="2%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" width="3%">$</td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: right" valign="bottom" width="4%">82.9</td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td></tr><tr bgcolor="#e2eef5"><td style="LINE-HEIGHT: 1.5" valign="bottom" align="left" width="15%"><div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5; MARGIN-RIGHT: 0pt" align="left">   Commodity derivatives</div></td><td style="LINE-HEIGHT: 1.5" valign="bottom" align="left" width="2%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" width="3%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: right" valign="bottom" width="4%">21.3</td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="LINE-HEIGHT: 1.5" valign="bottom" align="left" width="2%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" width="3%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: right" valign="bottom" width="4%">35.7</td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="LINE-HEIGHT: 1.5" valign="bottom" align="left" width="2%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" width="3%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: right" valign="bottom" width="4%">9.3</td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="LINE-HEIGHT: 1.5" valign="bottom" align="left" width="2%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" width="3%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: right" valign="bottom" width="4%">66.3</td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td></tr><tr bgcolor="white"><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5" valign="bottom" align="left" width="15%"><div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5; MARGIN-RIGHT: 0pt" align="left">   Interest rate derivative</div></td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5" valign="bottom" align="left" width="2%"> </td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 2px solid; TEXT-ALIGN: left" valign="bottom" width="3%"> </td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 2px solid; TEXT-ALIGN: right" valign="bottom" width="4%">-</td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5" valign="bottom" align="left" width="2%"> </td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 2px solid; TEXT-ALIGN: left" valign="bottom" width="3%"> </td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 2px solid; TEXT-ALIGN: right" valign="bottom" width="4%">1.0</td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5" valign="bottom" align="left" width="2%"> </td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 2px solid; TEXT-ALIGN: left" valign="bottom" width="3%"> </td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 2px solid; TEXT-ALIGN: right" valign="bottom" width="4%">-</td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5" valign="bottom" align="left" width="2%"> </td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 2px solid; TEXT-ALIGN: left" valign="bottom" width="3%"> </td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 2px solid; TEXT-ALIGN: right" valign="bottom" width="4%">1.0</td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td></tr><tr bgcolor="#e2eef5"><td style="PADDING-BOTTOM: 4px; LINE-HEIGHT: 1.5" valign="bottom" width="15%">  </td><td style="PADDING-BOTTOM: 4px; LINE-HEIGHT: 1.5" valign="bottom" align="left" width="2%"> </td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 4px double; TEXT-ALIGN: left" valign="bottom" width="3%">$</td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 4px double; TEXT-ALIGN: right" valign="bottom" width="4%">104.2</td><td style="PADDING-BOTTOM: 4px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="PADDING-BOTTOM: 4px; LINE-HEIGHT: 1.5" valign="bottom" align="left" width="2%"> </td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 4px double; TEXT-ALIGN: left" valign="bottom" width="3%">$</td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 4px double; TEXT-ALIGN: right" valign="bottom" width="4%">36.7</td><td style="PADDING-BOTTOM: 4px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="PADDING-BOTTOM: 4px; LINE-HEIGHT: 1.5" valign="bottom" align="left" width="2%"> </td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 4px double; TEXT-ALIGN: left" valign="bottom" width="3%">$</td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 4px double; TEXT-ALIGN: right" valign="bottom" width="4%">9.3</td><td style="PADDING-BOTTOM: 4px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="PADDING-BOTTOM: 4px; LINE-HEIGHT: 1.5" valign="bottom" align="left" width="2%"> </td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 4px double; TEXT-ALIGN: left" valign="bottom" width="3%">$</td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 4px double; TEXT-ALIGN: right" valign="bottom" width="4%">150.2</td><td style="PADDING-BOTTOM: 4px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td></tr><tr bgcolor="white"><td style="LINE-HEIGHT: 1.5" valign="bottom" align="left" width="15%"><div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5; MARGIN-RIGHT: 0pt" align="left">Liabilities</div></td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5" valign="bottom" width="2%"> </td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" width="3%"> </td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5; TEXT-ALIGN: right" valign="bottom" width="4%"> </td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5" valign="bottom" width="2%"> </td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" width="3%"> </td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5; TEXT-ALIGN: right" valign="bottom" width="4%"> </td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5" valign="bottom" width="2%"> </td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" width="3%"> </td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5; TEXT-ALIGN: right" valign="bottom" width="4%"> </td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5" valign="bottom" width="2%"> </td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" width="3%"> </td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5; TEXT-ALIGN: right" valign="bottom" width="4%"> </td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td></tr><tr bgcolor="#e2eef5"><td style="LINE-HEIGHT: 1.5" valign="bottom" align="left" width="15%"><div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5; MARGIN-RIGHT: 0pt" align="left">   Commodity derivatives</div></td><td style="LINE-HEIGHT: 1.5" valign="bottom" align="left" width="2%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" width="3%">$</td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: right" valign="bottom" width="4%">55.4</td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="LINE-HEIGHT: 1.5" valign="bottom" align="left" width="2%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" width="3%">$</td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: right" valign="bottom" width="4%">31.3</td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="LINE-HEIGHT: 1.5" valign="bottom" align="left" width="2%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" width="3%">$</td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: right" valign="bottom" width="4%">12.3</td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="LINE-HEIGHT: 1.5" valign="bottom" align="left" width="2%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" width="3%">$</td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: right" valign="bottom" width="4%">99.0</td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td></tr><tr bgcolor="white"><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5" valign="bottom" align="left" width="15%"><div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5; MARGIN-RIGHT: 0pt" align="left">   Interest rate derivative</div></td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5" valign="bottom" width="2%"> </td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 2px solid; TEXT-ALIGN: left" valign="bottom" width="3%"> </td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 2px solid; TEXT-ALIGN: right" valign="bottom" width="4%">-</td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5" valign="bottom" align="left" width="2%"> </td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 2px solid; TEXT-ALIGN: left" valign="bottom" width="3%"> </td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 2px solid; TEXT-ALIGN: right" valign="bottom" width="4%">3.2</td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5" valign="bottom" width="2%"> </td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 2px solid; TEXT-ALIGN: left" valign="bottom" width="3%"> </td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 2px solid; TEXT-ALIGN: right" valign="bottom" width="4%">-</td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5" valign="bottom" align="left" width="2%"> </td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 2px solid; TEXT-ALIGN: left" valign="bottom" width="3%"> </td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 2px solid; TEXT-ALIGN: right" valign="bottom" width="4%">3.2</td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td></tr><tr bgcolor="#e2eef5"><td style="PADDING-BOTTOM: 4px; LINE-HEIGHT: 1.5" valign="bottom" width="15%">  </td><td style="PADDING-BOTTOM: 4px; LINE-HEIGHT: 1.5" valign="bottom" align="left" width="2%"> </td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 4px double; TEXT-ALIGN: left" valign="bottom" width="3%">$</td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 4px double; TEXT-ALIGN: right" valign="bottom" width="4%">55.4</td><td style="PADDING-BOTTOM: 4px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="PADDING-BOTTOM: 4px; LINE-HEIGHT: 1.5" valign="bottom" align="left" width="2%"> </td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 4px double; TEXT-ALIGN: left" valign="bottom" width="3%">$</td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 4px double; TEXT-ALIGN: right" valign="bottom" width="4%">34.5</td><td style="PADDING-BOTTOM: 4px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="PADDING-BOTTOM: 4px; LINE-HEIGHT: 1.5" valign="bottom" align="left" width="2%"> </td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 4px double; TEXT-ALIGN: left" valign="bottom" width="3%">$</td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 4px double; TEXT-ALIGN: right" valign="bottom" width="4%">12.3</td><td style="PADDING-BOTTOM: 4px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="PADDING-BOTTOM: 4px; LINE-HEIGHT: 1.5" valign="bottom" align="left" width="2%"> </td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 4px double; TEXT-ALIGN: left" valign="bottom" width="3%">$</td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 4px double; TEXT-ALIGN: right" valign="bottom" width="4%">102.2</td><td style="PADDING-BOTTOM: 4px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td></tr><tr bgcolor="white"><td style="LINE-HEIGHT: 1.5" valign="bottom" width="15%">  </td><td style="LINE-HEIGHT: 1.5" valign="bottom" width="2%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" width="3%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: right" valign="bottom" width="4%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="LINE-HEIGHT: 1.5" valign="bottom" width="2%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" width="3%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: right" valign="bottom" width="4%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="LINE-HEIGHT: 1.5" valign="bottom" width="2%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" width="3%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: right" valign="bottom" width="4%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="LINE-HEIGHT: 1.5" valign="bottom" width="2%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" width="3%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: right" valign="bottom" width="4%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td></tr><tr bgcolor="#e2eef5"><td style="LINE-HEIGHT: 1.5" valign="bottom" align="left" width="54%" colspan="16"><div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5; MARGIN-RIGHT: 0pt" align="left">December 31, 2009</div></td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td></tr><tr bgcolor="white"><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5" valign="bottom" align="left" width="54%" colspan="16"><div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5; MARGIN-RIGHT: 0pt" align="left">Assets</div></td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td></tr><tr bgcolor="#e2eef5"><td style="LINE-HEIGHT: 1.5" valign="bottom" align="left" width="15%"><div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5; MARGIN-RIGHT: 0pt" align="left">   Money market funds</div></td><td style="LINE-HEIGHT: 1.5" valign="bottom" align="left" width="2%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" width="3%">$</td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: right" valign="bottom" width="4%">121.1</td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="LINE-HEIGHT: 1.5" valign="bottom" align="left" width="2%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" width="3%">$</td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: right" valign="bottom" width="4%">-</td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="LINE-HEIGHT: 1.5" valign="bottom" align="left" width="2%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" width="3%">$</td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: right" valign="bottom" width="4%">-</td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="LINE-HEIGHT: 1.5" valign="bottom" align="left" width="2%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" width="3%">$</td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: right" valign="bottom" width="4%">121.1</td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td></tr><tr bgcolor="white"><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5" valign="bottom" align="left" width="15%"><div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5; MARGIN-RIGHT: 0pt" align="left">   Commodity derivatives</div></td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5" valign="bottom" align="left" width="2%"> </td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 2px solid; TEXT-ALIGN: left" valign="bottom" width="3%"> </td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 2px solid; TEXT-ALIGN: right" valign="bottom" width="4%">14.6</td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5" valign="bottom" align="left" width="2%"> </td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 2px solid; TEXT-ALIGN: left" valign="bottom" width="3%"> </td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 2px solid; TEXT-ALIGN: right" valign="bottom" width="4%">16.8</td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5" valign="bottom" align="left" width="2%"> </td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 2px solid; TEXT-ALIGN: left" valign="bottom" width="3%"> </td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 2px solid; TEXT-ALIGN: right" valign="bottom" width="4%">8.8</td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5" valign="bottom" align="left" width="2%"> </td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 2px solid; TEXT-ALIGN: left" valign="bottom" width="3%"> </td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 2px solid; TEXT-ALIGN: right" valign="bottom" width="4%">40.2</td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td></tr><tr bgcolor="#e2eef5"><td style="PADDING-BOTTOM: 4px; LINE-HEIGHT: 1.5" valign="bottom" width="15%">  </td><td style="PADDING-BOTTOM: 4px; LINE-HEIGHT: 1.5" valign="bottom" align="left" width="2%"> </td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 4px double; TEXT-ALIGN: left" valign="bottom" width="3%">$</td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 4px double; TEXT-ALIGN: right" valign="bottom" width="4%">135.7</td><td style="PADDING-BOTTOM: 4px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="PADDING-BOTTOM: 4px; LINE-HEIGHT: 1.5" valign="bottom" align="left" width="2%"> </td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 4px double; TEXT-ALIGN: left" valign="bottom" width="3%">$</td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 4px double; TEXT-ALIGN: right" valign="bottom" width="4%">16.8</td><td style="PADDING-BOTTOM: 4px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="PADDING-BOTTOM: 4px; LINE-HEIGHT: 1.5" valign="bottom" align="left" width="2%"> </td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 4px double; TEXT-ALIGN: left" valign="bottom" width="3%">$</td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 4px double; TEXT-ALIGN: right" valign="bottom" width="4%">8.8</td><td style="PADDING-BOTTOM: 4px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="PADDING-BOTTOM: 4px; LINE-HEIGHT: 1.5" valign="bottom" align="left" width="2%"> </td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 4px double; TEXT-ALIGN: left" valign="bottom" width="3%">$</td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 4px double; TEXT-ALIGN: right" valign="bottom" width="4%">161.3</td><td style="PADDING-BOTTOM: 4px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td></tr><tr bgcolor="white"><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5" valign="bottom" align="left" width="54%" colspan="16"><div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5; MARGIN-RIGHT: 0pt" align="left">Liabilities</div></td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td></tr><tr bgcolor="#e2eef5"><td style="LINE-HEIGHT: 1.5" valign="bottom" align="left" width="15%"><div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5; MARGIN-RIGHT: 0pt" align="left">   Commodity derivatives</div></td><td valign="bottom" align="left" width="2%"> </td><td style="TEXT-ALIGN: left" valign="bottom" width="3%">$</td><td style="TEXT-ALIGN: right" valign="bottom" width="4%">54.2</td><td style="TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td valign="bottom" align="left" width="2%"> </td><td style="TEXT-ALIGN: left" valign="bottom" width="3%">$</td><td style="TEXT-ALIGN: right" valign="bottom" width="4%">29.3</td><td style="TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td valign="bottom" align="left" width="2%"> </td><td style="TEXT-ALIGN: left" valign="bottom" width="3%">$</td><td style="TEXT-ALIGN: right" valign="bottom" width="4%">3.8</td><td style="TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td valign="bottom" align="left" width="2%"> </td><td style="TEXT-ALIGN: left" valign="bottom" width="3%">$</td><td style="TEXT-ALIGN: right" valign="bottom" width="4%">87.3</td><td style="TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td></tr></table></div><div style="DISPLAY: block; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5"> </div><div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5; MARGIN-RIGHT: 0pt" align="left">When available and appropriate, the company uses quoted market prices in active markets to determine fair value and classifies such items within Level 1.  For derivatives, Level 1 values include only those derivative instruments traded on the NYMEX.  The company enters into over-the-counter instruments with values that are similar to, and correlate with, quoted prices for exchange-traded instruments in active markets; the fair values of these over-the-counter items consider credit risk and are classified within Level 2.  In certain instances, the company may be required to determine a fair value using significant unobservable inputs such as indicative broker prices; the resulting valuation is classified as Level 3.</div><div style="DISPLAY: block; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5"> </div><div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5; MARGIN-RIGHT: 0pt" align="left">A description of the company’s objectives and strategies for using derivative instruments, and related accounting policies, is included in Note 2 – Accounting Policies – Derivative instruments and Credit risk and concentrations.</div><div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5; MARGIN-RIGHT: 0pt" align="left"> </div><div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5; MARGIN-RIGHT: 0pt" align="left">The following table presents a reconciliation of the Level 3 beginning and ending net derivative asset (liability) balances for the periods ended December 31 (in millions):</div><div style="DISPLAY: block; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5"> </div><div style="LINE-HEIGHT: 1.5" align="center"><table style="FONT-SIZE: 10pt; FONT-FAMILY: times new roman" cellspacing="0" cellpadding="0" width="100%"><tr><td style="PADDING-BOTTOM: 2px" valign="bottom" width="32%">  </td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5" valign="bottom" width="1%"> </td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 2px solid" valign="bottom" width="7%" colspan="2"><div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5; MARGIN-RIGHT: 0pt" align="center">2010</div></td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5" valign="bottom" width="1%"> </td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 2px solid" valign="bottom" width="7%" colspan="2"><div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5; MARGIN-RIGHT: 0pt" align="center">2009</div></td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td></tr><tr><td style="LINE-HEIGHT: 1.5" valign="bottom" width="32%">  </td><td style="LINE-HEIGHT: 1.5" valign="bottom" width="1%"> </td><td style="LINE-HEIGHT: 1.5" valign="bottom" width="7%" colspan="2"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="LINE-HEIGHT: 1.5" valign="bottom" width="1%"> </td><td style="LINE-HEIGHT: 1.5" valign="bottom" width="7%" colspan="2"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td></tr><tr><td style="LINE-HEIGHT: 1.5" valign="bottom" align="left" width="32%"><div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5; MARGIN-RIGHT: 0pt" align="left">Beginning of period</div></td><td style="LINE-HEIGHT: 1.5" valign="bottom" align="left" width="1%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" width="1%">$</td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: right" valign="bottom" width="6%">5.0</td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="LINE-HEIGHT: 1.5" valign="bottom" align="left" width="1%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" width="1%">$</td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: right" valign="bottom" width="6%">1.6</td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td></tr><tr bgcolor="#e2eef5"><td style="PADDING-LEFT: 0pt; MARGIN-LEFT: 9pt; LINE-HEIGHT: 1.5" valign="bottom" align="left" width="32%"><div style="DISPLAY: block; MARGIN-LEFT: 9pt; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5; MARGIN-RIGHT: 0pt" align="left">Net realized/unrealized gains (losses)</div></td><td style="LINE-HEIGHT: 1.5" valign="bottom" width="1%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" width="1%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: right" valign="bottom" width="6%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="LINE-HEIGHT: 1.5" valign="bottom" width="1%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" width="1%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: right" valign="bottom" width="6%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td></tr><tr bgcolor="white"><td style="PADDING-LEFT: 0pt; MARGIN-LEFT: 446pt; LINE-HEIGHT: 1.5" valign="bottom" align="left" width="32%"><div style="DISPLAY: block; MARGIN-LEFT: 18pt; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5; MARGIN-RIGHT: 0pt" align="left">Included in regulatory assets and liabilities</div></td><td style="LINE-HEIGHT: 1.5" valign="bottom" align="left" width="1%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" width="1%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: right" valign="bottom" width="6%">(.6</td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%">)</td><td style="LINE-HEIGHT: 1.5" valign="bottom" align="left" width="1%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" width="1%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: right" valign="bottom" width="6%">(3.5</td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%">)</td></tr><tr bgcolor="#e2eef5"><td style="PADDING-LEFT: 0pt; MARGIN-LEFT: 446pt; LINE-HEIGHT: 1.5" valign="bottom" align="left" width="32%"><div style="DISPLAY: block; MARGIN-LEFT: 18pt; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5; MARGIN-RIGHT: 0pt" align="left">Included in net income</div></td><td style="LINE-HEIGHT: 1.5" valign="bottom" align="left" width="1%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" width="1%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: right" valign="bottom" width="6%">(1.5</td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%">)</td><td style="LINE-HEIGHT: 1.5" valign="bottom" align="left" width="1%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" width="1%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: right" valign="bottom" width="6%">15.2</td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td></tr><tr bgcolor="white"><td style="PADDING-LEFT: 0pt; MARGIN-LEFT: 446pt; LINE-HEIGHT: 1.5" valign="bottom" align="left" width="32%"><div style="DISPLAY: block; MARGIN-LEFT: 9pt; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5; MARGIN-RIGHT: 0pt" align="left">Settlements, net of purchases and issuances</div></td><td style="LINE-HEIGHT: 1.5" valign="bottom" align="left" width="1%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" width="1%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: right" valign="bottom" width="6%">5.7</td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="LINE-HEIGHT: 1.5" valign="bottom" align="left" width="1%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" width="1%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: right" valign="bottom" width="6%">(2.0</td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%">)</td></tr><tr bgcolor="#e2eef5"><td style="PADDING-LEFT: 0pt; MARGIN-LEFT: 446pt; LINE-HEIGHT: 1.5" valign="bottom" align="left" width="32%"><div style="DISPLAY: block; MARGIN-LEFT: 9pt; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5; MARGIN-RIGHT: 0pt" align="left">Transfers into Level 3</div></td><td style="LINE-HEIGHT: 1.5" valign="bottom" align="left" width="1%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" width="1%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: right" valign="bottom" width="6%">(9.8</td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%">)</td><td style="LINE-HEIGHT: 1.5" valign="bottom" align="left" width="1%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" width="1%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: right" valign="bottom" width="6%">5.4</td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td></tr><tr bgcolor="white"><td style="PADDING-LEFT: 0pt; PADDING-BOTTOM: 2px; MARGIN-LEFT: 446pt; LINE-HEIGHT: 1.5" valign="bottom" align="left" width="32%"><div style="DISPLAY: block; MARGIN-LEFT: 9pt; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5; MARGIN-RIGHT: 0pt" align="left">Transfers out of Level 3</div></td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5" valign="bottom" align="left" width="1%"> </td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 2px solid; TEXT-ALIGN: left" valign="bottom" width="1%"> </td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 2px solid; TEXT-ALIGN: right" valign="bottom" width="6%">(1.8</td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%">)</td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5" valign="bottom" align="left" width="1%"> </td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 2px solid; TEXT-ALIGN: left" valign="bottom" width="1%"> </td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 2px solid; TEXT-ALIGN: right" valign="bottom" width="6%">(11.7</td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%">)</td></tr><tr bgcolor="#e2eef5"><td style="PADDING-BOTTOM: 4px; LINE-HEIGHT: 1.5" valign="bottom" align="left" width="32%"><div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5; MARGIN-RIGHT: 0pt" align="left">End of period</div></td><td style="PADDING-BOTTOM: 4px; LINE-HEIGHT: 1.5" valign="bottom" align="left" width="1%"> </td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 4px double; TEXT-ALIGN: left" valign="bottom" width="1%">$</td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 4px double; TEXT-ALIGN: right" valign="bottom" width="6%">(3.0</td><td style="PADDING-BOTTOM: 4px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%">)</td><td style="PADDING-BOTTOM: 4px; LINE-HEIGHT: 1.5" valign="bottom" align="left" width="1%"> </td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 4px double; TEXT-ALIGN: left" valign="bottom" width="1%">$</td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 4px double; TEXT-ALIGN: right" valign="bottom" width="6%">5.0</td><td style="PADDING-BOTTOM: 4px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td></tr><tr bgcolor="white"><td style="LINE-HEIGHT: 1.5" valign="bottom" width="32%">  </td><td style="LINE-HEIGHT: 1.5" valign="bottom" width="1%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" width="1%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: right" valign="bottom" width="6%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="LINE-HEIGHT: 1.5" valign="bottom" width="1%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" width="1%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: right" valign="bottom" width="6%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td></tr><tr bgcolor="#e2eef5"><td style="LINE-HEIGHT: 1.5" valign="bottom" align="left" width="32%"><div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5; MARGIN-RIGHT: 0pt" align="left">Net unrealized gains (losses) included in net income above relating to derivatives still held at December 31</div></td><td valign="bottom" align="left" width="1%"> </td><td style="TEXT-ALIGN: left" valign="bottom" width="1%">$</td><td style="TEXT-ALIGN: right" valign="bottom" width="6%">(2.3</td><td style="TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%">)</td><td valign="bottom" align="left" width="1%"> </td><td style="TEXT-ALIGN: left" valign="bottom" width="1%">$</td><td style="TEXT-ALIGN: right" valign="bottom" width="6%">5.0</td><td style="TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td></tr></table></div><div style="DISPLAY: block; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5"> </div><div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5; MARGIN-RIGHT: 0pt" align="left">Net realized/unrealized gains (losses) included in net income are attributable to Nicor Enerchange and are classified as operating revenues.</div><div style="DISPLAY: block; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5"> </div><div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5; MARGIN-RIGHT: 0pt" align="left">Transfers into and out of Level 3 reflect the liquidity at the relevant natural gas trading locations and dates which affects the significance of unobservable inputs used in the valuation.  In 2010, in accordance with new accounting guidance, the company elected to determine both transfers into and out of Level 3 using values at the end of the interim period in which the transfer occurred.  In 2009, transfers into Level 3 were determined using beginning of period values and transfers out of Level 3 were determined using end of period values.</div><div style="DISPLAY: block; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5"> </div><div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5; MARGIN-RIGHT: 0pt" align="left">Nicor maintains margin accounts related to financial derivative transactions.  The company’s policy is not to offset the fair value of assets and liabilities recognized for derivative instruments or any related margin account.  The following table represents the balance sheet classification of margin accounts related to derivative instruments at December 31 (in millions):</div><div style="DISPLAY: block; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5"> </div><div style="LINE-HEIGHT: 1.5" align="center"><table style="FONT-SIZE: 10pt; FONT-FAMILY: times new roman" cellspacing="0" cellpadding="0" width="100%"><tr><td style="PADDING-BOTTOM: 2px" valign="bottom" width="32%">  </td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5" valign="bottom" width="1%"> </td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 2px solid" valign="bottom" width="7%" colspan="2"><div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5; MARGIN-RIGHT: 0pt" align="center">2010</div></td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5" valign="bottom" width="1%"> </td><td style="LINE-HEIGHT: 1.5; BORDER-BOTTOM: black 2px solid" valign="bottom" width="7%" colspan="2"><div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5; MARGIN-RIGHT: 0pt" align="center">2009</div></td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td></tr><tr bgcolor="#e2eef5"><td style="LINE-HEIGHT: 1.5" valign="bottom" align="left" width="32%"><div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5; MARGIN-RIGHT: 0pt" align="left">Assets</div></td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5" valign="bottom" width="1%"> </td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5" valign="bottom" width="7%" colspan="2"> </td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5" valign="bottom" width="1%"> </td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5" valign="bottom" width="7%" colspan="2"> </td><td style="PADDING-BOTTOM: 2px; LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td></tr><tr bgcolor="white"><td style="LINE-HEIGHT: 1.5" valign="bottom" align="left" width="32%"><div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 18pt; LINE-HEIGHT: 1.5; MARGIN-RIGHT: 0pt" align="left">Margin accounts - derivative instruments</div></td><td style="LINE-HEIGHT: 1.5" valign="bottom" align="left" width="1%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" width="1%">$</td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: right" valign="bottom" width="6%">50.9</td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="LINE-HEIGHT: 1.5" valign="bottom" align="left" width="1%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" width="1%">$</td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: right" valign="bottom" width="6%">46.1</td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td></tr><tr bgcolor="#e2eef5"><td style="LINE-HEIGHT: 1.5" valign="bottom" align="left" width="32%"><div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 18pt; LINE-HEIGHT: 1.5; MARGIN-RIGHT: 0pt" align="left">Other - noncurrent</div></td><td style="LINE-HEIGHT: 1.5" valign="bottom" align="left" width="1%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" width="1%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: right" valign="bottom" width="6%">8.1</td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td><td style="LINE-HEIGHT: 1.5" valign="bottom" align="left" width="1%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" width="1%"> </td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: right" valign="bottom" width="6%">13.8</td><td style="LINE-HEIGHT: 1.5; TEXT-ALIGN: left" valign="bottom" nowrap="nowrap" width="1%"> </td></tr></table></div><div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5; MARGIN-RIGHT: -5.4pt" align="left"> </div><div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; LINE-HEIGHT: 1.5; MARGIN-RIGHT: -5.4pt" align="left">In addition, the recorded amount of restricted short and long-term investments and short-term borrowings approximates fair value.  Long-term debt outstanding is recorded at the principal balance outstanding, net of unamortized discounts.  The principal balance of Nicor Gas’ First Mortgage Bonds outstanding at December 31, 2010 and 2009 was $500 million.  Based on quoted prices or market interest rates, the fair value of the company’s First Mortgage Bonds was approximately $554 million and $543 million at December 31, 2010 and 2009, respectively.</div><div> </div>7.FAIR VALUE MEASUREMENTSThe fair value of assets and liabilities that are measured on a recurring basis are categorized in the table below (in millions) intofalsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringThis element represents the disclosure related to the fair value measurement of assets and liabilities which includes [financial] instruments measured at fair value that are classified in stockholders' equity. Such assets and liabilities may be measured on a recurring or nonrecurring basis. The disclosures which may be required or desired include: (1) for assets and liabilities measured on a recurring basis, disclosure may include: (a) the fair value measurements at the reporting date; (b) the level within the fair value hierarchy in which the fair value measurements in their entirety fall, segregating fair value measurements using quoted prices in active markets for identical assets or liabilities (Level 1), significant other observable inputs (Level 2), and significant unobservable inputs (Level 3); (c) for fair value measurements using significant unobservable inputs (Level 3), a reconciliation of the beginning and ending balances, separately presenting changes during the period attributable to the following: (i) total gains or losses for the period (realized and unrealized), segregating those gains or losses included in earnings (or changes in net assets), and a description of where those gains or losses included in earnings (or changes in net assets) are reported in the statement of income (or activities); (ii) purchases, sales, issuances, and settlements (net); (iii) transfers in and transfers out of Level 3 (for example, transfers due to changes in the observability of significant inputs); (d) the amount of the total gains or losses for the period in subparagraph (c) (i) above included in earnings (or changes in net assets) that are attributable to the change in unrealized gains or losses relating to those assets and liabilities still held at the reporting date and a description of where those unrealized gains or losses are reported in the statement of income (or activities); (e) the valuation technique(s) used to measure fair value and a discussion of changes in valuation techniques, if any, during the period and (2) for assets and liabilities that are measured at fair value on a nonrecurring basis (for example, impaired assets) disclosure may include, in addition to (a) above: (a) the reasons for the fair value measurements recorded; (b) the same as (b) above; (c) for fair value measurements using significant unobservable inputs (Level 3), a description of the inputs and the information used to develop the inputs; and (d) the valuation technique(s) used to measure fair value and a discussion of changes, if any, in the valuation technique(s) used to measure similar assets and/or liabilities in prior periods.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 157 -Paragraph 32 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 157 -Paragraph 33 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 157 -Paragraph 6 -Footnote 4 falsefalseFAIR VALUE MEASUREMENTS12FAIR VALUE MEASUREMENTSUnKnownUnKnownUnKnownUnKnownfalsetrue