Statement of Other Comprehensive Income (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Accumulated net gain (loss) on cash flow derivative hedges at beginning of year	$ (33,258)	$ 42,848	$ 166,028
Net (loss) gain on cash flow derivative hedges	58,138	70,480	(54,877)
Net (gain) loss reclassified into earnings	(109,385)	(146,586)	(68,303)
Accumulated net gain (loss) on cash flow derivative hedges at end of year	(84,505)	(33,258)	42,848
Accumulated other comprehensive gain at beginning of the year	(75,938)
Current-period change	(58,578)	(101,004)	(157,667)
Accumulated other comprehensive gain at end of year	(134,516)	(75,938)
Changes related to cash flow derivative hedges
Accumulated other comprehensive gain at beginning of the year	(33,258)
Current-period change	(51,247)
Accumulated other comprehensive gain at end of year	(84,505)
Change in defined benefit plans
Accumulated other comprehensive gain at beginning of the year	(30,256)
Current-period change	(4,567)
Accumulated other comprehensive gain at end of year	(34,823)
Foreign currency translation adjustments
Accumulated other comprehensive gain at beginning of the year	(12,424)
Current-period change	(2,764)
Accumulated other comprehensive gain at end of year	$ (15,188)