Long-term Funding (Textual) (Details) - USD ($) $ in Millions	1 Months Ended
	Nov. 30, 2014	Dec. 31, 2017	Dec. 31, 2016
Subordinated Borrowing [Line Items]
Federal Home Loan Bank, Advances, Weighted Average Interest Rate		1.26%	0.50%
Long-term Federal Home Loan Bank Advances		$ 6,600
Federal Home Loan Bank Advances		$ 3,200
Two Thousand Fourteen Senior Notes [Member]
Subordinated Borrowing [Line Items]
New Senior Debt Issued	$ 250
Debt Instrument, Interest Rate, Stated Percentage	2.75%
Two Thousand Fourteen Subordinated Notes [Member]
Subordinated Borrowing [Line Items]
Junior Subordinated Debentures Issued	$ 250
Debt Instrument, Term	10 years
Subordinated Borrowing, Interest Rate	4.25%