Short and Long-Term Funding (Long-term Funding Narrative) (Details) - USD ($) $ in Millions	1 Months Ended
	Nov. 30, 2014	Jun. 30, 2017	Dec. 31, 2016
Subordinated Borrowing [Line Items]
Carrying Value of Securities Purchased under Agreements to Resell and Deposits Paid for Securities Borrowed		$ 381
Federal Home Loan Bank, Advances, Weighted Average Interest Rate		0.98%	0.50%
Two Thousand Fourteen Senior Notes
Subordinated Borrowing [Line Items]
New Senior Debt Issued	$ 250
Debt Instrument, Interest Rate, Stated Percentage	2.75%
Two Thousand Fourteen Subordinated Notes
Subordinated Borrowing [Line Items]
Junior Subordinated Debentures Issued	$ 250
Debt Instrument, Term	10 years
Subordinated Borrowing, Interest Rate	4.25%