Fair Value Measurements (Carrying Amount And Estimated Fair Values Of Financial Instruments) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative instruments, net	$ (375)	$ (2)
Carrying Amount [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	1,423	15
Credit facility		116
Derivative instruments, net	(375)	(2)
Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	1,423	15
Credit facility		116
Derivative instruments, net	(375)	(2)
Unsecured Debt [Member] | Carrying Amount [Member] | Term Loan 1 due December 2020 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans	327	750
Unsecured Debt [Member] | Carrying Amount [Member] | Term Loan 2 due December 2020 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans	1,191
Unsecured Debt [Member] | Fair Value [Member] | Term Loan 1 due December 2020 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans	327	$ 750
Unsecured Debt [Member] | Fair Value [Member] | Term Loan 2 due December 2020 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans	$ 1,191
Long-term Debt [Member] | Term Loan 1 due December 2020 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Maturity date, year and month	2020-12	2018-11
Accelerated maturity date, year and month if not amended, redeemed or refinanced	2019-10
Long-term Debt [Member] | Term Loan 2 due December 2020 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Maturity date, year and month	2020-12
Accelerated maturity date, year and month if not amended, redeemed or refinanced	2019-10
Long-term Debt [Member] | 2020 Senior Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Maturity date, year and month	2020-01
Amount to be amended, redeemed or refinanced to avoid acceleration	$ 765
Senior Notes [Member] | Carrying Amount [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Senior notes	3,166	$ 3,867
Senior Notes [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Senior notes	$ 3,182	$ 2,672