Changes in Accumulated Other Comprehensive Income (Loss) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 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	(57,344)	(11,574)
Amounts reclassified from accumulated other comprehensive loss	4,868	(15,270)
Total other comprehensive loss	(52,476)	(26,844)
Ending balance	(46,805)	(161,360)
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	(57,352)	(7,330)
Amounts reclassified from accumulated other comprehensive loss	4,437	(15,270)
Total other comprehensive loss	(52,915)	(22,600)
Ending balance	(9,591)	(107,105)
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	(2,462)	0
Amounts reclassified from accumulated other comprehensive loss	431	0
Total other comprehensive loss	(2,031)	0
Ending balance	(26,025)	(34,823)
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	2,470	(4,244)
Amounts reclassified from accumulated other comprehensive loss	0	0
Total other comprehensive loss	2,470	(4,244)
Ending balance	$ (11,189)	$ (19,432)