Changes in Accumulated Other Comprehensive (Loss) Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Changes in accumulated other comprehensive loss by component
Accumulated comprehensive loss at beginning of the year	$ (1,328,433)	$ (896,994)
Other comprehensive (loss) income before reclassifications	(96,808)	(355,983)
Amounts reclassified from accumulated other comprehensive loss	102,681	61,997
Total other comprehensive income (loss)	5,873	(293,986)
Ending balance	(1,322,560)	(1,190,980)
Changes related to cash flow derivative hedges
Changes in accumulated other comprehensive loss by component
Accumulated comprehensive loss at beginning of the year	(1,232,073)	(826,026)
Other comprehensive (loss) income before reclassifications	(99,659)	(322,383)
Amounts reclassified from accumulated other comprehensive loss	102,396	61,434
Total other comprehensive income (loss)	2,737	(260,949)
Ending balance	(1,229,336)	(1,086,975)
Changes in defined benefit plans
Changes in accumulated other comprehensive loss by component
Accumulated comprehensive loss at beginning of the year	(26,447)	(31,207)
Other comprehensive (loss) income before reclassifications	(3,797)	(2,056)
Amounts reclassified from accumulated other comprehensive loss	285	563
Total other comprehensive income (loss)	(3,512)	(1,493)
Ending balance	(29,959)	(32,700)
Foreign currency translation adjustments
Changes in accumulated other comprehensive loss by component
Accumulated comprehensive loss at beginning of the year	(69,913)	(39,761)
Other comprehensive (loss) income before reclassifications	6,648	(31,544)
Amounts reclassified from accumulated other comprehensive loss	0	0
Total other comprehensive income (loss)	6,648	(31,544)
Ending balance	$ (63,265)	$ (71,305)