Stockholders' Equity and EPS - Activity Related to Net Gains on Cash Flow Hedges in AOCI (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cash flow hedge gains expected to reclassified out of AOCI over next 12 months	$ 59
Balance, beginning of period, net of tax	11,967	$ 7,468	$ 8,433	$ 6,621
Balance, end of period, net of tax	14,669	7,967	14,669	7,967
Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning of period, net of tax	107	153	129	(2)
Net increase in fair value, net of tax	0	0	0	168
Net realized gain reclassified to net income, net of tax	(12)	(12)	(34)	(25)
Balance, end of period, net of tax	$ 95	$ 141	$ 95	$ 141