Short-term Borrowings (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Borrowings
Amount of the company's liability including accrued interest	$ 200	$ 500
Repurchase Agreements
Borrowings
Fair value of securities pledged	51	52
Amount of the company's liability including accrued interest	50	50
Weighted average annual interest rate (as a percent)	0.30%	0.30%
Federal Home Loan Bank (FHLB) Advances
Borrowings
Fair value of securities pledged	502	574
Amount of the company's liability including accrued interest	$ 150	$ 450
Weighted average annual interest rate (as a percent)	0.30%	0.30%