Consolidated Statements of Shareholder's Equity - USD ($) $ in Millions	Total	Cumulative Effect, Period of Adoption, Adjustment [Member]		Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Loss [Member]	Retained Earnings [Member]	Retained Earnings [Member] Cumulative Effect, Period of Adoption, Adjustment [Member]
Beginning balance at Dec. 31, 2017	$ 1,871			$ 0	$ 161	$ (998)	$ 2,708
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	387						387
Other comprehensive loss	(62)					(62)
Ending balance at Dec. 31, 2018	2,196			0	161	(1,060)	3,095
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	418						418
Other comprehensive loss	(27)					(27)
Ending balance at Dec. 31, 2019	2,587	$ 119	[1]	0	161	(1,087)	3,513	$ 119	[1]
Ending balance at Jan. 01, 2020								119
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Impact of new accounting guidance, tax		21
Beginning balance at Dec. 31, 2019	$ 2,587	119	[1]	0	161	(1,087)	3,513	$ 119	[1]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member
Net income	$ 201						201
Other comprehensive loss	(12)					(12)
Ending balance at Dec. 31, 2020	$ 2,895			$ 0	$ 161	$ (1,099)	$ 3,833
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Impact of new accounting guidance		$ 140

[1] Represents $140 million, net of tax of $21 million, related to the impact as of January 1, 2020, of adopting the new accounting guidance for the recognition of credit losses on certain financial instruments.