Assets Purchased under Resale Agreements and Sold under Repurchase Agreements (Resale Agreements and Repurchase Agreements) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Resale agreements
Gross resale agreements	$ 1,310,000		$ 1,310,000		$ 1,160,000
Loans purchased under agreements to resell, increase	989,200		989,200		300,000
Repurchase agreements
Gross repurchase agreements	$ 300,000		$ 300,000		$ 300,000
Weighted average interest rates	2.63%	3.40%	2.65%	3.76%
Securities Purchased Under Resale Agreements
Resale agreements
Weighted-average yields	1.54%	2.14%	1.55%	2.32%
Loans Purchased Under Resale Agreements
Resale agreements
Weighted-average yields	1.47%		1.64%