Short and Long-Term Funding FHLB Maturity Schedule (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
FHLB_Maturity_ [Line Items]
FHLB advances	$ 2,877,727	$ 3,574,371
Weighted Average Contractual Coupon Rate	2.28%	2.19%
Maturity or put date 1 year or less
FHLB_Maturity_ [Line Items]
FHLB advances	$ 2,376,052	$ 2,262,584
Weighted Average Contractual Coupon Rate	2.24%	2.06%
After 1 but within 2
FHLB_Maturity_ [Line Items]
FHLB advances	$ 288,174	$ 1,285,039
Weighted Average Contractual Coupon Rate	2.57%	2.39%
After 2 but within 3
FHLB_Maturity_ [Line Items]
FHLB advances	$ 5,781	$ 14,393
Weighted Average Contractual Coupon Rate	5.11%	2.98%
After 3 years
FHLB_Maturity_ [Line Items]
FHLB advances	$ 207,720	$ 12,354
Weighted Average Contractual Coupon Rate	2.30%	4.55%