Other Comprehensive Income (Schedule of Changes in Accumulated Other Comprehensive Income by Component) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Beginning Balance	$ (73)	$ (63)
Other comprehensive (loss) income before reclassifications	(26)	(14)
Amounts reclassified from accumulated other comprehensive income (loss)	10	7
Other comprehensive loss	(16)	(7)
Accumulated Other Comprehensive Income (Loss), Ending Balance	(89)	(70)
Change in Fair Value of Interest Rate Swaps [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Beginning Balance	(48)	(43)
Other comprehensive (loss) income before reclassifications	(28)	(15)
Amounts reclassified from accumulated other comprehensive income (loss)	9	6
Other comprehensive loss	(19)	(9)
Accumulated Other Comprehensive Income (Loss), Ending Balance	(67)	(52)
Change in Fair Value of Available for Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Beginning Balance	1	7
Other comprehensive (loss) income before reclassifications	2	$ 1
Amounts reclassified from accumulated other comprehensive income (loss)
Other comprehensive loss	2	$ 1
Accumulated Other Comprehensive Income (Loss), Ending Balance	3	8
Change in Unrecognized Pension Cost Components [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Beginning Balance	(26)	(27)
Amounts reclassified from accumulated other comprehensive income (loss)	1	1
Other comprehensive loss	1	1
Accumulated Other Comprehensive Income (Loss), Ending Balance	$ (25)	$ (26)