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	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment
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	384					384
Total other comprehensive income	45				45
Shares issued from Employee Stock Purchase Plan (in shares)			149,789
Stock-based compensation (in shares)			368,862
Stock-based compensation	10			10
Dividends declared and paid (in shares)			583
Dividends declared and paid	(9)					(9)
Ending balance (in shares) at Sep. 30, 2020			57,150,470
Ending balance at Sep. 30, 2020	2,195		$ 1	1,493	46	655
Beginning balance (in shares) at Jun. 30, 2020			56,943,979
Beginning balance at Jun. 30, 2020	1,971		$ 1	1,488	46	436
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	222					222
Total other comprehensive income	0
Shares issued from Employee Stock Purchase Plan (in shares)			43,946
Stock-based compensation (in shares)			162,371
Stock-based compensation	5			5
Dividends declared and paid (in shares)			174
Dividends declared and paid	(3)					(3)
Ending balance (in shares) at Sep. 30, 2020			57,150,470
Ending balance at Sep. 30, 2020	2,195		$ 1	1,493	46	655
Beginning balance (in shares) at Dec. 31, 2020			52,656,067
Beginning balance at Dec. 31, 2020	2,201		$ 1	1,346	47	807
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	448					448
Total other comprehensive income	(9)				(9)
Shares issued from Employee Stock Purchase Plan (in shares)			106,707
Stock-based compensation (in shares)			99,255
Stock-based compensation	16			16
Dividends declared and paid (in shares)			354
Dividends declared and paid	(11)					(11)
Ending balance (in shares) at Sep. 30, 2021			52,862,383
Ending balance at Sep. 30, 2021	2,645		$ 1	1,362	38	1,244
Beginning balance (in shares) at Jun. 30, 2021			52,862,264
Beginning balance at Jun. 30, 2021	2,498		$ 1	1,356	45	1,096
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	152					152
Total other comprehensive income	(7)				(7)
Stock-based compensation	6			6
Dividends declared and paid (in shares)			119
Dividends declared and paid	(4)					(4)
Ending balance (in shares) at Sep. 30, 2021			52,862,383
Ending balance at Sep. 30, 2021	$ 2,645		$ 1	$ 1,362	$ 38	$ 1,244