Derivative Financial Instruments - Offsetting of Derivative Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Derivatives not subject to master netting arrangements
Gross amounts of recognized assets	$ 155,587	$ 77,277
Derivatives subject to master netting arrangements:
Gross amounts of recognized assets	42,804	46,039
Gross amounts offset in the consolidated balance sheet	34,557	(26,969)
Net amounts of assets presented in the consolidated balance sheet	77,361	19,070
Total
Gross amounts of recognized assets	198,391	123,316
Net amounts of assets presented in the balance sheet	232,948	96,347
Interest rate lock commitments
Derivatives not subject to master netting arrangements
Gross amounts of recognized assets	147,400	50,507
Total
Net amounts of assets presented in the balance sheet	147,400	50,507
Repurchase agreement derivatives
Derivatives not subject to master netting arrangements
Gross amounts of recognized assets	8,187	26,770
MBS put options
Derivatives subject to master netting arrangements:
Gross amounts of recognized assets	10,040	720
Net amounts of assets presented in the consolidated balance sheet	10,040	720
Total
Gross amounts of recognized assets	10,040	720
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
Total
Gross amounts of recognized assets		2,135
Forward contracts | Purchases
Derivatives subject to master netting arrangements:
Gross amounts of recognized assets	17,943	35,916
Net amounts of assets presented in the consolidated balance sheet	17,943	35,916
Total
Gross amounts of recognized assets	17,943	35,916
Forward contracts | Sales
Derivatives subject to master netting arrangements:
Gross amounts of recognized assets	6,141	437
Net amounts of assets presented in the consolidated balance sheet	6,141	437
Total
Gross amounts of recognized assets	6,141	437
Put options on interest rate futures | Purchases
Derivatives subject to master netting arrangements:
Gross amounts of recognized assets	6,266	866
Net amounts of assets presented in the consolidated balance sheet	6,266	866
Total
Gross amounts of recognized assets	6,266	866
Call options on interest rate futures | Purchases
Derivatives subject to master netting arrangements:
Gross amounts of recognized assets	2,414	5,965
Net amounts of assets presented in the consolidated balance sheet	2,414	5,965
Total
Gross amounts of recognized assets	$ 2,414	$ 5,965