Consolidated Statements of Stockholders' Equity - USD ($) $ in Millions		Total	Cumulative Effect, Period of Adoption, Adjustment	Common Stock	Additional Paid in Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment
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		(2)					(2)
Repurchase of shares (in shares)	[1]			(1,329,657)
Repurchase of shares	[1]	(50)			(50)
Ending balance (in shares) at Mar. 31, 2019				56,480,086
Ending balance at Mar. 31, 2019		1,574		$ 1	1,476	(31)	128
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		97
Total other comprehensive income		39
Ending balance (in shares) at Jun. 30, 2019				56,483,937
Ending balance at Jun. 30, 2019		1,656		$ 1	1,477	(8)	186
Beginning balance (in shares) at Mar. 31, 2019				56,480,086
Beginning balance at Mar. 31, 2019		1,574		$ 1	1,476	(31)	128
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		61					61
Total other comprehensive income		23				23
Shares issued from Employee Stock Purchase Plan (in shares)				26,785
Shares issued from Employee Stock Purchase Plan		0
Stock-based compensation (in shares)				164,926
Stock-based compensation		1			1
Dividends declared and paid (in shares)				188
Dividends declared and paid		(3)					(3)
Repurchase of shares (in shares)	[1]			(188,048)
Repurchase of shares	[1]	0
Ending balance (in shares) at Jun. 30, 2019				56,483,937
Ending balance at Jun. 30, 2019		1,656		$ 1	1,477	(8)	186
Beginning balance (in shares) at Dec. 31, 2019				56,631,236
Beginning balance at Dec. 31, 2019		1,788	$ (23)	$ 1	1,483	1	303	$ (23)
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)					(3)
Ending balance (in shares) at Mar. 31, 2020				56,729,789
Ending balance at Mar. 31, 2020		1,842		$ 1	1,487	31	323
Beginning balance (in shares) at Dec. 31, 2019				56,631,236
Beginning balance at Dec. 31, 2019		1,788	$ (23)	$ 1	1,483	1	303	$ (23)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		161
Total other comprehensive income		45
Ending balance (in shares) at Jun. 30, 2020				56,943,979
Ending balance at Jun. 30, 2020		1,971		$ 1	1,488	46	436
Beginning balance (in shares) at Mar. 31, 2020				56,729,789
Beginning balance at Mar. 31, 2020		1,842		$ 1	1,487	31	323
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		116					116
Total other comprehensive income		15				15
Shares issued from Employee Stock Purchase Plan (in shares)				46,591
Shares issued from Employee Stock Purchase Plan		0
Stock-based compensation (in shares)				167,410
Stock-based compensation		1			1
Dividends declared and paid (in shares)				189
Dividends declared and paid		(3)					(3)
Repurchase of shares	[1]	0
Ending balance (in shares) at Jun. 30, 2020				56,943,979
Ending balance at Jun. 30, 2020		$ 1,971		$ 1	$ 1,488	$ 46	$ 436

[1] Includes dividend reinvestment shares