Changes in Accumulated Other Comprehensive Loss - Changes in AOCI by Component (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Changes in accumulated other comprehensive loss by component
Beginning balance	$ 8,760,669	$ 12,163,846
Ending balance	7,884,015	8,963,905
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	42,247	(221,571)
Amounts reclassified from accumulated other comprehensive loss	19,531	45,297
Net current-period other comprehensive income (loss)	61,778	(176,274)
Ending balance	(588,741)	(864,803)
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	5,085	(14,900)
Amounts reclassified from accumulated other comprehensive loss	2,290	1,033
Net current-period other comprehensive income (loss)	7,375	(13,867)
Ending balance	(58,167)	(59,425)
Foreign currency translation adjustments
Changes in accumulated other comprehensive loss by component
Beginning balance	(23,280)	(63,626)
Other comprehensive income (loss) before reclassifications	6,233	2,327
Amounts reclassified from accumulated other comprehensive loss	0	34,300
Net current-period other comprehensive income (loss)	6,233	36,627
Ending balance	(17,047)	(26,999)
Accumulated other comprehensive loss
Changes in accumulated other comprehensive loss by component
Beginning balance	(739,341)	(797,713)
Other comprehensive income (loss) before reclassifications	53,565	(234,144)
Amounts reclassified from accumulated other comprehensive loss	21,821	80,630
Net current-period other comprehensive income (loss)	75,386	(153,514)
Ending balance	$ (663,955)	$ (951,227)