Goodwill and Intangible Assets Goodwill and Intangible Assets (Summary of CDI Carrying Value and Amortization) (Details) - Core deposit intangible - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Acquired Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 34	$ 34
Accumulated amortization	(24)	(21)
Net carrying amount	$ 10	$ 13