Short and Long-term Funding FHLB Maturity Schedule (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
FHLB_Maturity_ [Line Items]
Federal Home Loan Bank, Advances, Branch of FHLB Bank, Amount of Advances		$ 1,632,723	$ 3,180,967
Increase Decrease in FHLB Advances		$ (1,500,000)
Weighted Average Coupon Rate		2.34%
Decrease in FHLB Advances, Percent		49.00%
Prepayment of FHLB advances	$ 950,000
Loss on prepayments of FHLB advances		$ 44,650
Increase Decrease in short-term FHLB Advances		$ (520,000)
Long term Funding Weighted Average Coupon Rate		3.83%
Maturity or put date 1 year or less
FHLB_Maturity_ [Line Items]
Federal Home Loan Bank, Advances, Branch of FHLB Bank, Amount of Advances		$ 17,723
Weighted Average Coupon Rate		2.25%
After 1 but within 2
FHLB_Maturity_ [Line Items]
Federal Home Loan Bank, Advances, Branch of FHLB Bank, Amount of Advances		$ 7,383
Weighted Average Coupon Rate		3.70%
After 2 but within 3
FHLB_Maturity_ [Line Items]
Federal Home Loan Bank, Advances, Branch of FHLB Bank, Amount of Advances		$ 2,398
Weighted Average Coupon Rate		5.09%