Derivative Activities - Offsetting of Derivative Assets - Derivative Assets, Financial Assets, and Collateral Held by Counterparty (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Total
Net amounts of assets presented in the balance sheet	$ 96,347	$ 78,179
Net amount		78,179
Deutsche Bank AG
Total
Net amounts of assets presented in the balance sheet	26,770	10,656
Net amount		10,656
RJ O'Brien
Total
Net amounts of assets presented in the balance sheet	6,831	4,508
Net amount		4,508
Citibank, N.A.
Total
Net amounts of assets presented in the balance sheet	2,488	472
Net amount		472
JP Morgan
Total
Net amounts of assets presented in the balance sheet	1,399	267
Net amount		267
Bank of America, N.A.
Total
Net amounts of assets presented in the balance sheet	2,781
Federal National Mortgage Association
Total
Net amounts of assets presented in the balance sheet	456	1,092
Net amount		1,092
Other
Total
Net amounts of assets presented in the balance sheet	1,408	1,172
Net amount		1,172
Wells Fargo Bank, N.A.
Total
Net amounts of assets presented in the balance sheet	3,707
Interest rate lock commitments
Total
Net amounts of assets presented in the balance sheet	$ 50,507	60,012
Net amount		$ 60,012