Changes in Accumulated Other Comprehensive Loss - Changes in AOCI by Component (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Changes in accumulated other comprehensive loss by component
Beginning balance	$ 8,760,669	$ 12,163,846
Ending balance	9,172,382	10,231,775
Changes related to cash flow derivative hedges
Changes in accumulated other comprehensive loss by component
Beginning balance	(650,519)	(688,529)
Other comprehensive income (loss) before reclassifications	(927)	(322,985)
Amounts reclassified from accumulated other comprehensive loss	11,229	22,380
Net current-period other comprehensive income (loss)	10,302	(300,605)
Ending balance	(640,217)	(989,134)
Changes in defined benefit plans
Changes in accumulated other comprehensive loss by component
Beginning balance	(65,542)	(45,558)
Other comprehensive income (loss) before reclassifications	9,720	(8,094)
Amounts reclassified from accumulated other comprehensive loss	743	505
Net current-period other comprehensive income (loss)	10,463	(7,589)
Ending balance	(55,079)	(53,147)
Foreign currency translation adjustments
Changes in accumulated other comprehensive loss by component
Beginning balance	(23,280)	(63,626)
Other comprehensive income (loss) before reclassifications	9,722	10,290
Amounts reclassified from accumulated other comprehensive loss	0	0
Net current-period other comprehensive income (loss)	9,722	10,290
Ending balance	(13,558)	(53,336)
Accumulated other comprehensive loss
Changes in accumulated other comprehensive loss by component
Beginning balance	(739,341)	(797,713)
Other comprehensive income (loss) before reclassifications	18,515	(320,789)
Amounts reclassified from accumulated other comprehensive loss	11,972	22,885
Net current-period other comprehensive income (loss)	30,487	(297,904)
Ending balance	$ (708,854)	$ (1,095,617)

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

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