Derivative Activities - Offsetting of Derivative Assets - Derivative Assets, Financial Assets, and Collateral Held by Counterparty (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Total
Net amounts of assets presented in the balance sheet	$ 121,153	$ 96,347
Net amount	121,153	96,347
Deutsche Bank AG
Total
Net amounts of assets presented in the balance sheet	24,632	26,770
Net amount	24,632	26,770
RJ O'Brien
Total
Net amounts of assets presented in the balance sheet	16,717	6,831
Net amount	16,717	6,831
Wells Fargo Bank, N.A.
Total
Net amounts of assets presented in the balance sheet	2,275	3,707
Net amount	2,275	3,707
Bank of America, N.A.
Total
Net amounts of assets presented in the balance sheet	4,052	2,781
Net amount	4,052	2,781
Citibank, N.A.
Total
Net amounts of assets presented in the balance sheet		2,488
Net amount		2,488
JP Morgan
Total
Net amounts of assets presented in the balance sheet	3,494	1,399
Net amount	3,494	1,399
Goldman Sachs
Total
Net amounts of assets presented in the balance sheet	1,286
Net amount	1,286
Other
Total
Net amounts of assets presented in the balance sheet	449	1,864
Net amount	449	1,864
Interest rate lock commitments
Total
Net amounts of assets presented in the balance sheet	68,248	50,507
Net amount	$ 68,248	$ 50,507