Fair Value Fair Value Measurement (Narratives) (Details) (HARP loans [Member], USD $) In Billions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Changes due to new accounting guidance or enhanced fair value estimation process [Line Items]
Loans Receivable Refinanced under Home Affordable Refinance Program, Fair Value Disclosure	$ 303.6	$ 306.9
Fair Value Estimation Process [Member]
Changes due to new accounting guidance or enhanced fair value estimation process [Line Items]
Changes in estimated fair value	$ 10.1	$ 11.5