Consolidated Statement of Shareholder's Interest - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Shareholder's Interest [Roll Forward]
Balance at beginning of period	$ 5,227
Net income	21	$ 603
Other Comprehensive Income (Loss), Net of Tax	(348)	20
Distributions declared	275	675
Balance at end of period	5,227
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	13,543	14,923
Accounting Standards Update 2016-13 [Member]
Shareholder's Interest [Roll Forward]
Cumulative Effect of New Accounting Principle in Period of Adoption	(202)
Shareholder's Interest [Member]
Shareholder's Interest [Roll Forward]
Balance at beginning of period	5,227	5,227
Net income	0	0
Other Comprehensive Income (Loss), Net of Tax	0	0
Distributions declared	0	0
Balance at end of period	5,227	5,227
Shareholder's Interest [Member] | Accounting Standards Update 2016-13 [Member]
Shareholder's Interest [Roll Forward]
Cumulative Effect of New Accounting Principle in Period of Adoption	0
Accumulated Other Comprehensive Income/(Loss) (Note11) [Member]
Shareholder's Interest [Roll Forward]
Balance at beginning of period	(785)	(829)
Net income	0	0
Other Comprehensive Income (Loss), Net of Tax	(348)	20
Distributions declared	0	0
Balance at end of period	(1,133)	(809)
Accumulated Other Comprehensive Income/(Loss) (Note11) [Member] | Accounting Standards Update 2016-13 [Member]
Shareholder's Interest [Roll Forward]
Cumulative Effect of New Accounting Principle in Period of Adoption	0
Retained Earnings [Member]
Shareholder's Interest [Roll Forward]
Balance at beginning of period	9,905	10,577
Net income	21	603
Other Comprehensive Income (Loss), Net of Tax	0	0
Distributions declared	275	675
Balance at end of period	9,449	$ 10,505
Retained Earnings [Member] | Accounting Standards Update 2016-13 [Member]
Shareholder's Interest [Roll Forward]
Cumulative Effect of New Accounting Principle in Period of Adoption	$ (202)