Basis of Presentation Basis of Presentation (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Basis of Presentation [Abstract]
Cash and Cash Equivalents, at Carrying Value	$ 1,258,000,000	$ 534,000,000	$ 1,258,000,000	$ 534,000,000	$ 686,000,000
Program cash	79,000,000	48,000,000	79,000,000	48,000,000	211,000,000
Restricted Cash and Cash Equivalents	2,000,000	3,000,000	2,000,000	3,000,000
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	1,339,000,000	585,000,000	1,339,000,000	585,000,000	900,000,000	$ 735,000,000
Net Unrealized Gain Or Loss Of Foreign Currency Transactions On Intercompany Loan Hedges			6,000,000	3,000,000
Proceeds from Sale of Equity Method Investments				64,000,000
Gain (Loss) on Sale of Equity Investments				44,000,000
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	53,000,000		53,000,000		56,000,000
Equity Securities without Readily Determinable Fair Value, Amount					8,000,000
Equity Securities without Readily Determinable Fair Value, Upward Price Adjustment, Cumulative Amount	12,000,000		12,000,000
Other related Revenue	22,000,000	33,000,000	54,000,000	63,000,000
Adjustments related to New Accounting Pronouncements [Line Items]
Long-term Debt, Gross	1,200,000,000		1,200,000,000
Revenues	760,000,000	2,337,000,000	2,513,000,000	4,257,000,000
Operating Lease, Right-of-Use Asset	2,714,000,000		2,714,000,000		2,596,000,000
Line of Credit Facility, Current Borrowing Capacity	1,800,000,000		1,800,000,000
Cash and cash equivalents	1,258,000,000	534,000,000	1,258,000,000	534,000,000	686,000,000
Cash and Cash Equivalents [Abstract]
Adjusted EBITDA	(382,000,000)	175,000,000	(469,000,000)	174,000,000
Income (Loss) from Equity Method Investments, Net of Dividends or Distributions			1,000,000	4,000,000
Derivatives not designated as hedging instruments	(28,000,000)	(13,000,000)	(10,000,000)	(1,000,000)
Property leases [Member]
Adjustments related to New Accounting Pronouncements [Line Items]
Operating Lease, Right-of-Use Asset	2,714,000,000		2,714,000,000		$ 2,596,000,000
Americas [Member]
Adjustments related to New Accounting Pronouncements [Line Items]
Revenues	565,000,000	1,627,000,000	1,822,000,000	2,954,000,000
EMEA [Member]
Adjustments related to New Accounting Pronouncements [Line Items]
Revenues	159,000,000	572,000,000	516,000,000	1,005,000,000
Asia and Australasia [Member]
Adjustments related to New Accounting Pronouncements [Line Items]
Revenues	$ 36,000,000	$ 138,000,000	$ 175,000,000	$ 298,000,000