Accumulated Other Comprehensive Income - Changes in Accumulated Balances of Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Accumulated Other Comprehensive Income (Loss), Tax
Beginning balance	$ 25	$ 16	$ 25	$ 24
Other comprehensive income (loss) before reclassifications	9	(12)	5	(27)
Less: Amount of gain (loss) reclassified from AOCI	(1)	(4)	(5)	(11)
Net current period other comprehensive income (loss)	10	(8)	10	(16)
Ending balance	35	8	35	8
Accumulated Other Comprehensive Income (Loss), Net of Tax
Beginning balance			2,870
Other comprehensive income (loss) before reclassifications	95	(88)	45	(95)
Less: Amount of gain (loss) reclassified from AOCI	5	15	18	42
Other comprehensive income (loss), net of tax	90	(103)	27	(137)
Ending balance	2,920	3,270	2,920	3,270
Unrealized Gains (Losses) on Derivative Instruments
Accumulated Other Comprehensive Income (Loss), Before Tax
Beginning balance	(9)	38	(9)	68
Other comprehensive income (loss) before reclassifications	(35)	54	(18)	58
Less: Amount of gain (loss) reclassified from AOCI	6	19	23	53
Net current period other comprehensive income (loss)	(41)	35	(41)	5
Ending balance	(50)	73	(50)	73
Unrealized Gains (Losses) on Investments
Accumulated Other Comprehensive Income (Loss), Before Tax
Beginning balance	6	0	5	(56)
Other comprehensive income (loss) before reclassifications	0	3	1	59
Less: Amount of gain (loss) reclassified from AOCI	0	0	0	0
Net current period other comprehensive income (loss)	0	3	1	59
Ending balance	6	3	6	3
Foreign Currency Translation
Accumulated Other Comprehensive Income (Loss), Before Tax
Beginning balance	299	410	363	462
Other comprehensive income (loss) before reclassifications	121	(133)	57	(185)
Less: Amount of gain (loss) reclassified from AOCI	0	0	0	0
Net current period other comprehensive income (loss)	121	(133)	57	(185)
Ending balance	420	277	420	277
Total
Accumulated Other Comprehensive Income (Loss), Net of Tax
Beginning balance	321	464	384	498
Ending balance	$ 411	$ 361	$ 411	$ 361