Condensed Consolidated Statement of Changes in Stockholders' Equity - USD ($) $ in Millions	Total	Class B Common Stock	Common Stock	Common Stock Class B Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock
Beginning balance at Dec. 31, 2017	$ 1,363				$ 926	$ 926	$ (42)	$ (447)
Beginning balance, shares at Dec. 31, 2017			135,617,263	12,799,999				(9,474,490)
Net income	105					105
Cumulative effect adjustment from adoption of new accounting guidance	4					4
Other comprehensive loss	(14)						(14)
Issuance of common stock related to exercises of options and vesting of RSUs	3				3
Issuance of common stock related to exercises of options and vesting of RSUs, shares			1,252,620
Repurchase of common stock (Note 13)	$ (100)							$ (100)
Repurchase of common stock, shares	(2,582,198)							(2,582,198)
Withholding taxes on net share settlements of equity awards	$ (19)				(19)
Stock-based compensation	100				100
Ending balance at Sep. 30, 2018	1,442				1,010	1,035	(56)	$ (547)
Ending balance, shares at Sep. 30, 2018			136,869,883	12,799,999				(12,056,688)
Beginning balance at Jun. 30, 2018	1,347				979	966	(51)	$ (547)
Beginning balance, shares at Jun. 30, 2018			136,778,032	12,799,999				(12,056,688)
Net income	69					69
Other comprehensive loss	$ (5)						(5)
Issuance of common stock related to exercises of options and vesting of RSUs, shares			91,851
Repurchase of common stock, shares	0
Withholding taxes on net share settlements of equity awards	$ (2)				(2)
Stock-based compensation	33				33
Ending balance at Sep. 30, 2018	1,442				1,010	1,035	(56)	$ (547)
Ending balance, shares at Sep. 30, 2018			136,869,883	12,799,999				(12,056,688)
Beginning balance at Dec. 31, 2018	$ 1,471				1,037	1,043	(62)	$ (547)
Beginning balance, shares at Dec. 31, 2018	125,101,322	12,799,999	137,158,010	12,799,999				(12,056,688)
Net income	$ 110					110
Cumulative effect adjustment from adoption of new accounting guidance	3					3
Other comprehensive loss	(13)						(13)
Issuance of common stock related to exercises of options and vesting of RSUs	$ 2				2
Issuance of common stock related to exercises of options and vesting of RSUs, shares			1,457,838
Repurchase of common stock, shares	0
Withholding taxes on net share settlements of equity awards	$ (28)				(28)
Stock-based compensation	103				103
Ending balance at Sep. 30, 2019	$ 1,648				1,114	1,156	(75)	$ (547)
Ending balance, shares at Sep. 30, 2019	126,559,160	12,799,999	138,615,848	12,799,999				(12,056,688)
Beginning balance at Jun. 30, 2019	$ 1,575				1,081	1,106	(65)	$ (547)
Beginning balance, shares at Jun. 30, 2019			138,525,158	12,799,999				(12,056,688)
Net income	50					50
Other comprehensive loss	$ (10)						(10)
Issuance of common stock related to exercises of options and vesting of RSUs, shares			90,690
Repurchase of common stock, shares	0
Withholding taxes on net share settlements of equity awards	$ (1)				(1)
Stock-based compensation	34				34
Ending balance at Sep. 30, 2019	$ 1,648				$ 1,114	$ 1,156	$ (75)	$ (547)
Ending balance, shares at Sep. 30, 2019	126,559,160	12,799,999	138,615,848	12,799,999				(12,056,688)