Consolidated Statement of Shareholder's Interest - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Shareholder's Interest [Roll Forward]
Net income	$ 407	$ 21	$ 613	$ 603	$ 428	$ 1,216
Other Comprehensive Income (Loss), Net of Tax	87	(348)	8	20
Distributions declared	275	275	650	675
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	13,762	13,543	14,894	14,923	13,762	14,894
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	5,227	5,227	5,227	5,227
Net income	0	0	0	0
Other Comprehensive Income (Loss), Net of Tax	0	0	0	0
Distributions declared	0	0	0	0
Balance at end of period	5,227	5,227	5,227	5,227	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	(1,133)	(785)	(809)	(829)	(785)	(829)
Net income	0	0	0	0
Other Comprehensive Income (Loss), Net of Tax	87	(348)	8	20
Distributions declared	0	0	0	0
Balance at end of period	(1,046)	(1,133)	(801)	(809)	(1,046)	(801)
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	9,449	9,905	10,505	10,577	9,905	10,577
Net income	407	21	613	603
Other Comprehensive Income (Loss), Net of Tax	0	0	0	0
Distributions declared	275	275	650	675
Balance at end of period	$ 9,581	9,449	$ 10,468	$ 10,505	$ 9,581	$ 10,468
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)