CONSOLIDATED STATEMENTS OF EQUITY AND REDEEMABLE NONCONTROLLING INTERESTS - USD ($) $ in Millions	Total	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Loss	Noncontrolling Interests	Class A Common Stock	Class A Common Stock Common Stock	Class B Common Stock	Class B Common Stock Common Stock
BALANCE at Dec. 31, 2018	$ 0
Increase (Decrease) in Temporary Equity
Issuance of redeemable subsidiary preferred equity, net of issuance costs	985
Noncontrolling interest issued or acquired	380
Distributions to redeemable noncontrolling interests	(14)
Net income (loss)	11
BALANCE at Sep. 30, 2019	1,362
BALANCE (shares) at Dec. 31, 2018							68,897,723		25,670,684
BALANCE at Dec. 31, 2018	1,600	$ 1,121	$ 518	$ (1)	$ (39)		$ 1		$ 0
Increase (Decrease) in Stockholders' Equity
Dividends declared and paid on Class A and Class B Common Stock	(55)		(55)
Class B Common Stock converted into Class A Common Stock (shares)							643,002		(643,002)
Class B Common Stock converted into Class A Common Stock	0
Repurchases of Class A Common Stock (shares)							(3,993,194)
Repurchases of Class A Common Stock	(125)	(125)
Class A Common Stock issued pursuant to employee benefit plans (shares)							1,515,606
Class A Common Stock issued pursuant to employee benefit plans	32	32
Noncontrolling interest issued or acquired	231				231
Distributions to noncontrolling interests, net	(15)				(15)
Net (loss) income	7		4		3
BALANCE (shares) at Sep. 30, 2019							67,063,137		25,027,682
BALANCE at Sep. 30, 2019	1,675	1,028	467	(1)	180		$ 1		$ 0
BALANCE at Jun. 30, 2019	0
Increase (Decrease) in Temporary Equity
Issuance of redeemable subsidiary preferred equity, net of issuance costs	985
Noncontrolling interest issued or acquired	380
Distributions to redeemable noncontrolling interests	(14)
Net income (loss)	11
BALANCE at Sep. 30, 2019	1,362
BALANCE (shares) at Jun. 30, 2019							67,032,088		25,027,682
BALANCE at Jun. 30, 2019	1,529	1,024	545	(1)	(40)		$ 1		$ 0
Increase (Decrease) in Stockholders' Equity
Dividends declared and paid on Class A and Class B Common Stock	(18)		(18)
Class A Common Stock issued pursuant to employee benefit plans (shares)							31,049
Class A Common Stock issued pursuant to employee benefit plans	4	4
Noncontrolling interest issued or acquired	231				231
Distributions to noncontrolling interests, net	(11)				(11)
Net (loss) income	(60)		(60)
BALANCE (shares) at Sep. 30, 2019							67,063,137		25,027,682
BALANCE at Sep. 30, 2019	1,675	1,028	467	(1)	180		$ 1		$ 0
BALANCE at Dec. 31, 2019	1,078
Increase (Decrease) in Temporary Equity
Noncontrolling interest issued or acquired	22
Distributions to noncontrolling interests, net	(32)
Distributions to redeemable noncontrolling interests	(378)
Redemption of redeemable noncontrolling interests	(547)
Net income (loss)	51
BALANCE at Sep. 30, 2020	194
BALANCE (shares) at Dec. 31, 2019						66,830,110	66,830,110	24,727,682	24,727,682
BALANCE at Dec. 31, 2019	1,694	1,011	492	(2)	192		$ 1		$ 0
Increase (Decrease) in Stockholders' Equity
Dividends declared and paid on Class A and Class B Common Stock	(49)		(49)
Repurchases of Class A Common Stock (shares)							(19,418,934)
Repurchases of Class A Common Stock	(343)	(343)
Class A Common Stock issued pursuant to employee benefit plans (shares)							1,759,674
Class A Common Stock issued pursuant to employee benefit plans	43	43
Noncontrolling interest issued or acquired	0
Distributions to noncontrolling interests, net	(19)				(19)
Distributions to redeemable noncontrolling interests	0
Redemption of redeemable noncontrolling interests	0
Other comprehensive loss	(9)			(9)
Net (loss) income	(2,994)		(2,881)		(113)
BALANCE (shares) at Sep. 30, 2020						49,170,850	49,170,850	24,727,682	24,727,682
BALANCE at Sep. 30, 2020	(1,677)	711	(2,438)	(11)	60		$ 1		$ 0
BALANCE at Jun. 30, 2020	510
Increase (Decrease) in Temporary Equity
Noncontrolling interest issued or acquired	22
Distributions to noncontrolling interests, net	(7)
Redemption of redeemable noncontrolling interests	(350)
Net income (loss)	19
BALANCE at Sep. 30, 2020	194
BALANCE (shares) at Jun. 30, 2020							53,342,336		24,727,682
BALANCE at Jun. 30, 2020	1,811	787	832	(11)	202		$ 1		$ 0
Increase (Decrease) in Stockholders' Equity
Dividends declared and paid on Class A and Class B Common Stock	(14)		(14)
Repurchases of Class A Common Stock (shares)							(4,274,004)
Repurchases of Class A Common Stock	(82)	(82)
Class A Common Stock issued pursuant to employee benefit plans (shares)							102,518
Class A Common Stock issued pursuant to employee benefit plans	6	6
Noncontrolling interest issued or acquired	0
Distributions to noncontrolling interests, net	(12)				(12)
Redemption of redeemable noncontrolling interests	0
Net (loss) income	(3,386)		(3,256)		(130)
BALANCE (shares) at Sep. 30, 2020						49,170,850	49,170,850	24,727,682	24,727,682
BALANCE at Sep. 30, 2020	$ (1,677)	$ 711	$ (2,438)	$ (11)	$ 60		$ 1		$ 0