Consolidated Statements of Stockholders' Equity - USD ($) $ in Millions		Total	CECL ASU Adjustment to RE	Common Stock	Additional Paid in Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings (Accumulated Deficit)	Retained Earnings (Accumulated Deficit) CECL ASU Adjustment to RE
Balance (in shares) at Dec. 31, 2017				57,321,228
Beginning balance at Dec. 31, 2017		$ 1,399		$ 1	$ 1,512	$ (16)	$ (98)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		187					187
Total other comprehensive income (loss)		(26)				(26)
Other comprehensive income (loss), net of tax		(31)
Shares issued for Employee Stock Purchase Plan (in shares)				114,385
Shares issued from the Employee Stock Purchase Plan		10			10
Stock-based compensation (in shares)				318,560
Reclassification of certain income tax effects	[1]	0				(5)	5
Repurchase of common shares (in shares)	[2]			(4,709)
Balance (in shares) at Dec. 31, 2018				57,749,464
Ending balance at Dec. 31, 2018		1,570		$ 1	1,522	(47)	94
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		218					218
Other comprehensive income (loss), net of tax		48				48
Shares issued for Employee Stock Purchase Plan (in shares)				106,881
Dividends declared and paid (in shares)				376
Dividends declared and paid		(9)					(9)
Stock-based compensation (in shares)				292,220
Stock-based compensation		11			11
Repurchase of common shares (in shares)	[2]			(1,517,705)
Repurchase of common shares	[2]	(50)			(50)
Balance (in shares) at Dec. 31, 2019				56,631,236
Ending balance at Dec. 31, 2019		1,788	$ (23)	$ 1	1,483	1	303	$ (23)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		538					538
Other comprehensive income (loss), net of tax		46				46
Shares issued for Employee Stock Purchase Plan (in shares)				181,875
Dividends declared and paid (in shares)				729
Dividends declared and paid		(11)					(11)
Stock-based compensation (in shares)				429,874
Stock-based compensation		$ 13			13
Repurchase of common shares (in shares)	[2]	(4,587,647)
Repurchase of common shares	[2]	$ (150)			(150)
Balance (in shares) at Dec. 31, 2020				52,656,067
Ending balance at Dec. 31, 2020		$ 2,201		$ 1	$ 1,346	$ 47	$ 807

[1] Income tax effects of the Tax Cuts and Jobs Act are reclassified from AOCI to retained earnings due to the adoption of ASU 2018-02.

[2] Includes dividend reinvestment shares.