Stockholders' Equity and EPS - Activity Related to Net Gains on Cash Flow Hedges in AOCI (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cash flow hedge gains expected to reclassified out of AOCI over next 12 months	$ 61
Balance, beginning of period, net of tax	10,121	$ 7,182	$ 8,433	$ 6,621
Balance, end of period, net of tax	11,967	7,468	11,967	7,468
Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning of period, net of tax	118	164	129	(2)
Net increase in fair value, net of tax	0	0	0	168
Net realized gain reclassified to net income, net of tax	(11)	(11)	(22)	(13)
Balance, end of period, net of tax	$ 107	$ 153	$ 107	$ 153