Transactions with Related Parties (Transactions with Other FHLBanks) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Related Party Transaction [Line Items]
ProceedsfromOtherFederalHomeLoanBanks	$ 25,000		$ 25,000	$ 500,000
Payments to other Federal Home Loan Banks	25,000		25,000	500,000
FHLBank of Chicago [Member]
Related Party Transaction [Line Items]
Servicing fee expense	988	$ 911	2,958	$ 2,613
Interest-bearing deposits maintained with FHLBank of Chicago	$ 7,291		$ 7,291		$ 5,173