Derivative Financial Instruments - Offsetting of Derivative Assets - Derivative Assets, Financial Assets, and Collateral Held by Counterparty (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Total
Net amounts of assets presented in the balance sheet	$ 578,254	$ 159,686
Net amount	578,254	159,686
JP Morgan
Total
Net amounts of assets presented in the balance sheet	18,772	2,196
Net amount	18,772	2,196
RJ O'Brien
Total
Net amounts of assets presented in the balance sheet	7,480	5,414
Net amount	7,480	5,414
Deutsche Bank AG
Total
Net amounts of assets presented in the balance sheet		9,138
Net amount		9,138
Wells Fargo Bank, N.A.
Total
Net amounts of assets presented in the balance sheet	5,256
Net amount	5,256
Mizuho Securities
Total
Net amounts of assets presented in the balance sheet		1,597
Net amount		1,597
Goldman Sachs
Total
Net amounts of assets presented in the balance sheet	1,148	2,548
Net amount	1,148	2,548
Other
Total
Net amounts of assets presented in the balance sheet	1,447	282
Net amount	1,447	282
Interest rate lock commitments
Total
Net amounts of assets presented in the balance sheet	544,151	138,511
Net amount	$ 544,151	$ 138,511