Long-term Funding, Composition (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Long-term Funding
FHLB advances	$ 2,900,168	$ 2,265,188
Senior notes, at par	250,000	250,000
Subordinated notes, at par	250,000	250,000
Other Long-term Debt and Capitalized Costs	(2,718)	(3,393)
Total long-term funding	$ 3,397,450	$ 2,761,795