Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012		Dec. 31, 2011		Mar. 31, 2011
Current assets:
Cash and cash equivalents	$ 91,389		$ 162,772		$ 136,016
Receivables, net	539,589		646,251		533,279
Inventories	313,341		274,205		262,696
Deferred income taxes	42,239		40,407		45,206
Commodity derivative instruments	26,698		27,687		13,250
Prepayments and other current assets	64,897		43,316		73,556
Total current assets	1,078,153		1,194,638		1,064,003
Investments	113,799		109,424		117,015
Property, plant and equipment	7,798,770		7,646,222		7,271,173
Less accumulated depreciation, depletion and amortization	3,419,574		3,361,208		3,174,654
Net property, plant and equipment	4,379,196		4,285,014		4,096,519
Deferred charges and other assets: [Abstract]
Goodwill	635,389	[1]	634,931	[1]	634,931	[1]
Other intangible assets, net	19,991		20,843		24,351
Other	312,103		311,275		254,472
Total deferred charges and other assets	967,483		967,049		913,754
Total assets	6,538,631		6,556,125		6,191,291
Current liabilities:
Long-term debt due within one year	202,215		139,267		12,785
Accounts payable	321,369		337,228		267,922
Taxes payable	51,019		70,176		49,852
Dividends payable	31,800		31,794		30,850
Accrued compensation	28,463		47,804		25,774
Commodity derivative instruments	20,183		13,164		40,499
Other accrued liabilities	255,172		259,320		227,088
Total current liabilities	910,221		898,753		654,770
Long-term debt	1,213,974		1,285,411		1,414,077
Deferred credits and other liabilities:
Deferred income taxes	798,669		769,166		701,933
Other liabilities	842,169		827,228		731,428
Total deferred credits and other liabilities	1,640,838		1,596,394		1,433,361
Stockholders' equity:
Preferred stocks	15,000		15,000		15,000
Common stockholders' equity:
Shares issued - 189,369,450 at March 31, 2012, 189,332,485 at March 31, 2011 and 189,332,485 at December 31, 2011	189,369		189,332		189,332
Other paid-in capital	1,035,800		1,035,739		1,032,040
Retained earnings	1,589,985		1,586,123		1,509,449
Accumulated other comprehensive loss	(52,930)		(47,001)		(53,112)
Treasury stock at cost - 538,921 shares	(3,626)		(3,626)		(3,626)
Total common stockholders' equity	2,758,598		2,760,567		2,674,083
Total stockholders' equity	2,773,598		2,775,567		2,689,083
Total liabilities and stockholders' equity	$ 6,538,631		$ 6,556,125		$ 6,191,291

[1] Balance is presented net of accumulated impairment of $12.3 million at the pipeline and energy services segment, which occurred in prior periods.