Fair Value (Available-for-sale Securities) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis, Total	$ 261	$ 258
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	17	25
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(7)	(3)
Available-for-sale Securities	271	280
Government and Corporate [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis, Total	161	161
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	1	3
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	(6)	(2)
Available-for-sale Securities, Debt Securities	156	162
Domestic [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Equity Securities, Amortized Cost Basis, Total	79	73
Available-for-sale Equity Securities, Accumulated Gross Unrealized Gain, before Tax	15	18
Available-for-sale Equity Securities, Accumulated Gross Unrealized Loss, before Tax	(1)
Available-for-sale Securities, Equity Securities	93	91
International [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Equity Securities, Amortized Cost Basis, Total	21	24
Available-for-sale Equity Securities, Accumulated Gross Unrealized Gain, before Tax	1	4
Available-for-sale Equity Securities, Accumulated Gross Unrealized Loss, before Tax		(1)
Available-for-sale Securities, Equity Securities	$ 22	$ 27