Changes in Accumulated Other Comprehensive (Loss) Income (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Changes in accumulated other comprehensive loss by component
Total other comprehensive (loss) income	$ (82,385)	$ 131,284	$ 69,065	$ 155,446
Changes related to cash flow derivative hedges
Changes in accumulated other comprehensive loss by component
Accumulated comprehensive loss at beginning of the year			(250,355)	(820,850)
Other comprehensive income (loss) before reclassifications			69,932	43,408
Amounts reclassified from accumulated other comprehensive loss			3,698	108,007
Total other comprehensive (loss) income			73,630	151,415
Ending balance	(176,725)	(669,435)	(176,725)	(669,435)
Changes in defined benefit plans
Changes in accumulated other comprehensive loss by component
Accumulated comprehensive loss at beginning of the year			(33,666)	(28,083)
Other comprehensive income (loss) before reclassifications			5,082	(4,847)
Amounts reclassified from accumulated other comprehensive loss			714	557
Total other comprehensive (loss) income			5,796	(4,290)
Ending balance	(27,870)	(32,373)	(27,870)	(32,373)
Foreign currency translation adjustments
Changes in accumulated other comprehensive loss by component
Accumulated comprehensive loss at beginning of the year			(50,244)	(67,551)
Other comprehensive income (loss) before reclassifications			(10,361)	8,321
Amounts reclassified from accumulated other comprehensive loss			0	0
Total other comprehensive (loss) income			(10,361)	8,321
Ending balance	(60,605)	(59,230)	(60,605)	(59,230)
Accumulated other comprehensive loss
Changes in accumulated other comprehensive loss by component
Accumulated comprehensive loss at beginning of the year			(334,265)	(916,484)
Other comprehensive income (loss) before reclassifications			64,653	46,882
Amounts reclassified from accumulated other comprehensive loss			4,412	108,564
Total other comprehensive (loss) income			69,065	155,446
Ending balance	$ (265,200)	$ (761,038)	$ (265,200)	$ (761,038)

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

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