Short and Long-Term Funding FHLB Maturity Schedule (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
FHLB_Maturity_ [Line Items]
FHLB advances	$ 2,742,941	$ 3,574,371
FHLB Weighted Average Coupon Rate	2.31%	2.19%
FHLB Maturity within One Year [Domain]
FHLB_Maturity_ [Line Items]
FHLB advances	$ 2,441,050	$ 2,262,584
FHLB Weighted Average Coupon Rate	2.27%	2.06%
FHLB Maturity One Year to Two Years [Domain]
FHLB_Maturity_ [Line Items]
FHLB advances	$ 288,248	$ 1,285,039
FHLB Weighted Average Coupon Rate	2.57%	2.39%
FHLB Maturity Over Two Years to Three Years [Domain]
FHLB_Maturity_ [Line Items]
FHLB advances	$ 4,811	$ 14,393
FHLB Weighted Average Coupon Rate	5.21%	2.98%
FHLB Maturity Over Three Years [Domain]
FHLB_Maturity_ [Line Items]
FHLB advances	$ 8,833	$ 12,354
FHLB Weighted Average Coupon Rate	3.36%	4.55%