Debt and Financing Arrangements (Tables)

12 Months Ended

Dec. 31, 2012

Debt Disclosure [Abstract]

Schedule of financing structure

	Outstanding(1)		Balance(2)
December 31, 2012
2006 Senior notes due 2016	$	500,000	$	499,347
2010 Senior notes due 2020		300,000		298,868
$1,000,000 Secured letter of credit facility - uncommitted		907,592		0
$450,000 Secured letter of credit facility - committed		108,853		0
	$	1,816,445	$	798,215
December 31, 2011
2006 Senior notes due 2016	$	500,000	$	499,194
2010 Senior notes due 2020		300,000		298,755
$900,000 Secured letter of credit facility - uncommitted		675,636		0
$400,000 Secured letter of credit facility - committed		141,351		0
$400,000 Unsecured letter of credit facility - committed		0		0
	$	1,616,987	$	797,949

• Indicates utilization of commitment amount, not drawn borrowings.
• Represents the principal amount borrowed, net of unamortized discount.

Schedule of debt maturities

	Amount
2013	$	0
2014		0
2015		0
2016		500,000
2017		0
2018 and thereafter		300,000
Total	$	800,000