Changes in Accumulated Other Comprehensive Income (Loss) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Changes in accumulated other comprehensive loss by component
Accumulated comprehensive loss at beginning of the year			$ 5,671	$ (134,516)
Other comprehensive income before reclassifications			(84,102)	16,250
Amounts reclassified from accumulated other comprehensive loss			7,101	(21,810)
Total other comprehensive (loss) income	(24,525)	21,284	(77,001)	(5,560)
Ending balance	(71,330)	(140,076)	(71,330)	(140,076)
Changes related to cash flow derivative hedges
Changes in accumulated other comprehensive loss by component
Accumulated comprehensive loss at beginning of the year			43,324	(84,505)
Other comprehensive income before reclassifications			(77,794)	18,046
Amounts reclassified from accumulated other comprehensive loss			4,241	(23,104)
Total other comprehensive (loss) income			(73,553)	(5,058)
Ending balance	(30,229)	(89,563)	(30,229)	(89,563)
Changes in defined benefit plans
Changes in accumulated other comprehensive loss by component
Accumulated comprehensive loss at beginning of the year			(23,994)	(34,823)
Other comprehensive income before reclassifications			(4,948)	3,999
Amounts reclassified from accumulated other comprehensive loss			863	1,294
Total other comprehensive (loss) income			(4,085)	5,293
Ending balance	(28,079)	(29,530)	(28,079)	(29,530)
Foreign currency translation adjustments
Changes in accumulated other comprehensive loss by component
Accumulated comprehensive loss at beginning of the year			(13,659)	(15,188)
Other comprehensive income before reclassifications			(1,360)	(5,795)
Amounts reclassified from accumulated other comprehensive loss			1,997	0
Total other comprehensive (loss) income			637	(5,795)
Ending balance	$ (13,022)	$ (20,983)	$ (13,022)	$ (20,983)