Changes in Accumulated Other Comprehensive Income (Loss) - Changes in AOCI by Component (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Changes in accumulated other comprehensive loss by component
Total other comprehensive loss	$ (74,193)	$ (82,385)	$ (25,439)	$ 69,065
Changes related to cash flow derivative hedges
Changes in accumulated other comprehensive loss by component
Accumulated comprehensive loss at beginning of the year			(537,216)	(250,355)
Other comprehensive income (loss) before reclassifications			(3,249)	69,932
Amounts reclassified from accumulated other comprehensive loss			(19,642)	3,698
Total other comprehensive loss			(22,891)	73,630
Ending balance	(560,107)	(176,725)	(560,107)	(176,725)
Changes in defined benefit plans
Changes in accumulated other comprehensive loss by component
Accumulated comprehensive loss at beginning of the year			(26,023)	(33,666)
Other comprehensive income (loss) before reclassifications			(10,758)	5,082
Amounts reclassified from accumulated other comprehensive loss			383	714
Total other comprehensive loss			(10,375)	5,796
Ending balance	(36,398)	(27,870)	(36,398)	(27,870)
Foreign currency translation adjustments
Changes in accumulated other comprehensive loss by component
Accumulated comprehensive loss at beginning of the year			(64,495)	(50,244)
Other comprehensive income (loss) before reclassifications			7,827	(10,361)
Amounts reclassified from accumulated other comprehensive loss			0	0
Total other comprehensive loss			7,827	(10,361)
Ending balance	(56,668)	(60,605)	(56,668)	(60,605)
Accumulated other comprehensive loss
Changes in accumulated other comprehensive loss by component
Accumulated comprehensive loss at beginning of the year			(627,734)	(334,265)
Other comprehensive income (loss) before reclassifications			(6,180)	64,653
Amounts reclassified from accumulated other comprehensive loss			(19,259)	4,412
Total other comprehensive loss			(25,439)	69,065
Ending balance	$ (653,173)	$ (265,200)	$ (653,173)	$ (265,200)

Amount after tax, before reclassification adjustments of other comprehensive income (loss).

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