Derivative Activities - Offsetting of Derivative Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Derivatives not subject to master netting arrangements
Gross amounts of recognized assets	$ 77,277	$ 70,668
Derivatives subject to master netting arrangements:
Gross amounts of recognized assets	46,039	14,378
Gross amounts offset in the consolidated balance sheet	(26,969)	(6,867)
Net amounts of assets presented in the consolidated balance sheet	19,070	7,511
Total
Gross amounts of recognized assets	123,316	85,046
Net amounts of assets presented in the balance sheet	96,347	78,179
Interest rate lock commitments
Derivatives not subject to master netting arrangements
Gross amounts of recognized assets	50,507	60,012
Total
Net amounts of assets presented in the balance sheet	50,507	60,012
Repurchase agreement derivatives
Derivatives not subject to master netting arrangements
Gross amounts of recognized assets	26,770	10,656
MBS put options
Derivatives subject to master netting arrangements:
Gross amounts of recognized assets	720	3,481
Net amounts of assets presented in the consolidated balance sheet	720	3,481
MBS call options
Derivatives subject to master netting arrangements:
Gross amounts of recognized assets	2,135
Net amounts of assets presented in the consolidated balance sheet	2,135
Forward contracts | Purchases
Derivatives subject to master netting arrangements:
Gross amounts of recognized assets	35,916	4,288
Net amounts of assets presented in the consolidated balance sheet	35,916	4,288
Forward contracts | Sales
Derivatives subject to master netting arrangements:
Gross amounts of recognized assets	437	2,101
Net amounts of assets presented in the consolidated balance sheet	437	2,101
Put options on interest rate futures | Purchases
Derivatives subject to master netting arrangements:
Gross amounts of recognized assets	866	3,570
Net amounts of assets presented in the consolidated balance sheet	866	3,570
Call options on interest rate futures | Purchases
Derivatives subject to master netting arrangements:
Gross amounts of recognized assets	5,965	938
Net amounts of assets presented in the consolidated balance sheet	$ 5,965	$ 938