Derivative Financial Instruments - Offsetting of Derivative Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Derivatives not subject to master netting arrangements
Gross amounts of recognized assets	$ 544,151	$ 146,698
Derivatives subject to master netting arrangements:
Gross amounts of recognized assets	138,931	40,699
Gross amounts offset in the consolidated balance sheet	(104,828)	(27,711)
Net amounts of assets presented in the consolidated balance sheet	34,103	12,988
Total
Gross amounts of recognized assets	683,082	187,397
Net amounts of assets presented in the balance sheet	578,254	159,686
Interest rate lock commitments
Derivatives not subject to master netting arrangements
Gross amounts of recognized assets	544,151	138,511
Total
Net amounts of assets presented in the balance sheet	544,151	138,511
Repurchase agreement derivatives
Derivatives not subject to master netting arrangements
Gross amounts of recognized assets		8,187
MBS put options
Derivatives subject to master netting arrangements:
Gross amounts of recognized assets	27,336	3,415
Net amounts of assets presented in the consolidated balance sheet	27,336	3,415
Total
Gross amounts of recognized assets	27,336	3,415
MBS call options
Derivatives subject to master netting arrangements:
Gross amounts of recognized assets	4,255
Net amounts of assets presented in the consolidated balance sheet	4,255
Total
Gross amounts of recognized assets	4,255
Swaptions
Derivatives subject to master netting arrangements:
Gross amounts of recognized assets	5,568	2,409
Net amounts of assets presented in the consolidated balance sheet	5,568	2,409
Swaptions | Purchases
Total
Gross amounts of recognized assets	5,568	2,409
Forward contracts | Purchases
Derivatives subject to master netting arrangements:
Gross amounts of recognized assets	72,640	12,364
Net amounts of assets presented in the consolidated balance sheet	72,640	12,364
Total
Gross amounts of recognized assets	72,640	12,364
Forward contracts | Sales
Derivatives subject to master netting arrangements:
Gross amounts of recognized assets	21,652	17,097
Net amounts of assets presented in the consolidated balance sheet	21,652	17,097
Total
Gross amounts of recognized assets	21,652	17,097
Put options on interest rate futures | Purchases
Derivatives subject to master netting arrangements:
Gross amounts of recognized assets	5,910	3,945
Net amounts of assets presented in the consolidated balance sheet	5,910	3,945
Total
Gross amounts of recognized assets	5,910	3,945
Call options on interest rate futures | Purchases
Derivatives subject to master netting arrangements:
Gross amounts of recognized assets	1,570	1,469
Net amounts of assets presented in the consolidated balance sheet	1,570	1,469
Total
Gross amounts of recognized assets	$ 1,570	$ 1,469