Principles of Consolidation and Other Matters - Investment Income (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Deferred Revenue Arrangement [Line Items]
Effective tax rate	27.90%	27.60%	28.60%	28.60%
Investment income (loss)	$ 3	$ (2)	$ 5	$ 11
Trident III [Member] | Private Equity Funds [Member]
Deferred Revenue Arrangement [Line Items]
Recognition of Deferred Revenue				$ 7