Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Millions	Total	Cumulative Effect, Period of Adoption, Adjustment Revision of Prior Period, Adjustment	Class B Common Stock	Common Stock	Additional Paid-in Capital	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment Revision of Prior Period, Adjustment	Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss) Cumulative Effect, Period of Adoption, Adjustment Revision of Prior Period, Adjustment	Treasury Stock
Beginning balance at Dec. 31, 2017	$ 1,363				$ 926	$ 926		$ (42)		$ (447)
Beginning balance, shares at Dec. 31, 2017			12,799,999	135,617,263						(9,474,490)
Net income (loss)	113					113
Cumulative effect adjustment from adoption of new accounting guidance at Dec. 31, 2017		$ 4					$ 4
Other comprehensive income (loss), net of tax	(20)							(20)
Issuance of common stock related to exercise of options and vesting of RSUs	6				6
Issuance of common stock related to exercise of options and vesting of RSUs, shares				1,540,747
Repurchase of common stock (Note 16)	$ (100)									$ (100)
Repurchase of common stock, shares	(2,582,198)									(2,582,198)
Withholding taxes on net share settlements of equity awards	$ (26)				(26)
Stock-based compensation	131				131
Ending balance at Dec. 31, 2018	1,471				1,037	1,043		(62)		$ (547)
Ending balance, shares at Dec. 31, 2018			12,799,999	137,158,010						(12,056,688)
Net income (loss)	126					126
Cumulative effect adjustment from adoption of new accounting guidance at Dec. 31, 2018		(1)							$ (1)
Other comprehensive income (loss), net of tax	3					3
Issuance of common stock related to exercise of options and vesting of RSUs	2				2
Issuance of common stock related to exercise of options and vesting of RSUs, shares				1,540,297
Repurchase of common stock (Note 16)	$ (60)									$ (60)
Repurchase of common stock, shares	(2,059,846)									(2,059,846)
Cash dividends declared to stockholders	$ (488)					(488)
Common stock dividend equivalents awarded to holders of nonvested restricted stock units	(3)					(3)
Withholding taxes on net share settlements of equity awards	(29)				(29)
Stock-based compensation	140				140
Ending balance at Dec. 31, 2019	$ 1,161				1,150	681		(63)		$ (607)
Ending balance, shares at Dec. 31, 2019	124,581,773		12,799,999	138,698,307						(14,116,534)
Net income (loss)	$ (289)					(289)
Cumulative effect adjustment from adoption of new accounting guidance at Dec. 31, 2019	681	$ (3)					$ (3)
Other comprehensive income (loss), net of tax	29							29
Issuance of common stock related to exercise of options and vesting of RSUs, shares				2,076,914
Repurchase of common stock (Note 16)	$ (115)									$ (115)
Repurchase of common stock, shares	(4,707,450)									(4,707,450)
Withholding taxes on net share settlements of equity awards	$ (21)				(21)
Stock-based compensation	124				124
Other, shares										(20,630)
Ending balance at Dec. 31, 2020	$ 886				$ 1,253	$ 389		$ (34)		$ (722)
Ending balance, shares at Dec. 31, 2020	121,930,607		12,799,999	140,775,221						(18,844,614)