Derivative Financial Instruments - Offsetting of Derivative Assets - Derivative Assets, Financial Assets, and Collateral Held by Counterparty (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Total
Net amounts of assets presented in the balance sheet	$ 433,211	$ 159,686
Net amount	433,211	159,686
JP Morgan
Total
Net amounts of assets presented in the balance sheet	27,313	2,196
Net amount	27,313	2,196
Citibank, N.A.
Total
Net amounts of assets presented in the balance sheet	9,995
Net amount	9,995
RJ O'Brien
Total
Net amounts of assets presented in the balance sheet	38,109	5,414
Net amount	38,109	5,414
Deutsche Bank AG
Total
Net amounts of assets presented in the balance sheet	7,894	9,138
Net amount	7,894	9,138
Wells Fargo Bank, N.A.
Total
Net amounts of assets presented in the balance sheet	5,848
Net amount	5,848
Daiwa Capital
Total
Net amounts of assets presented in the balance sheet	3,084
Net amount	3,084
Mizuho Securities
Total
Net amounts of assets presented in the balance sheet	2,989	1,597
Net amount	2,989	1,597
Federal National Mortgage Association
Total
Net amounts of assets presented in the balance sheet	1,980
Net amount	1,980
Goldman Sachs
Total
Net amounts of assets presented in the balance sheet	14,537	2,548
Net amount	14,537	2,548
Other
Total
Net amounts of assets presented in the balance sheet	3,841	282
Net amount	3,841	282
Interest rate lock commitments
Total
Net amounts of assets presented in the balance sheet	317,621	138,511
Net amount	$ 317,621	$ 138,511