Consolidated Statements of Stockholders' Equity - USD ($) $ in Millions	Total	Common Stock	Additional Paid in Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings (Accumulated Deficit)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
CECL ASU Adjustment to RE	$ 1,570	$ 1	$ 1,522	$ (47)	$ 94
Beginning balance (in shares) at Dec. 31, 2018		57,749,464
Beginning balance at Dec. 31, 2018	1,570	$ 1	1,522	(47)	94
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	36				36
Total other comprehensive income	16			16
Shares issued from Employee Stock Purchase Plan (in shares)		32,878
Shares issued from Employee Stock Purchase Plan	0
Stock-based compensation (in shares)		27,401
Stock-based compensation	4		4
Dividends declared and paid (in shares)		0
Dividends declared and paid	(2)				(2)
Repurchase of shares (in shares)		(1,329,657)
Repurchase of shares	(50)		(50)
CECL ASU Adjustment to RE	1,574	$ 1	1,476	(31)	128
Ending balance (in shares) at Mar. 31, 2019		56,480,086
Ending balance at Mar. 31, 2019	1,574	$ 1	1,476	(31)	128
Increase (Decrease) in Stockholders' Equity [Roll Forward]
CECL ASU Adjustment to RE	1,574	1	1,476	(31)	128
CECL ASU Adjustment to RE	1,788	$ 1	1,483	1	303
Beginning balance (in shares) at Dec. 31, 2019		56,631,236
Beginning balance at Dec. 31, 2019	1,788	$ 1	1,483	1	303
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	46				46
Total other comprehensive income	30			30
Shares issued from Employee Stock Purchase Plan (in shares)		59,252
Shares issued from Employee Stock Purchase Plan	0
Stock-based compensation (in shares)		(39,081)
Stock-based compensation	(4)		4
Dividends declared and paid (in shares)		(220)
Dividends declared and paid	(3)		0		(3)
CECL ASU Adjustment to RE	1,842	$ 1	1,487	31	323
Ending balance (in shares) at Mar. 31, 2020		56,729,789
Ending balance at Mar. 31, 2020	1,842	$ 1	1,487	31	323
Increase (Decrease) in Stockholders' Equity [Roll Forward]
CECL ASU Adjustment to RE	$ 1,842	$ 1	$ 1,487	$ 31	$ 323