Fair Value Measurements - Financial Instruments Carried at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Assets:
Loans, held for sale, at fair value	$ 306,328	$ 188,077
Derivative instruments, at fair value	17,756	2,814
Residential mortgage servicing rights, at fair value	78,631	91,174
Liabilities:
Derivative instruments, at fair value	16,585	5,250
Recurring
Assets:
Loans, held for sale, at fair value	310,345	192,510
Loans, net at fair value	19,813	20,212
Mortgage backed securities, at fair value	78,540	92,466
Derivative instruments, at fair value	17,756	2,814
Residential mortgage servicing rights, at fair value	78,631	91,174
Total assets	505,085	399,176
Liabilities:
Derivative instruments, at fair value	16,585	5,250
Total liabilities	16,585	5,250
Recurring | Level 2 inputs
Assets:
Loans, held for sale, at fair value	310,345	192,510
Mortgage backed securities, at fair value	78,437	92,006
Derivative instruments, at fair value	506
Total assets	389,288	284,516
Liabilities:
Derivative instruments, at fair value	16,585	5,250
Total liabilities	16,585	5,250
Recurring | Level 3 inputs
Assets:
Loans, net at fair value	19,813	20,212
Mortgage backed securities, at fair value	103	460
Derivative instruments, at fair value	17,250	2,814
Residential mortgage servicing rights, at fair value	78,631	91,174
Total assets	$ 115,797	$ 114,660