Fair Value of Financial Assets and Liabilities - Fair Value Hierarchy of Financial Assets and Liabilities under U.S. GAAP Guidance (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Assets:
Marketable securities		$ 36,795
Loans held for sale, at fair value	$ 1,089,429	215,290
Total assets	1,166,654	325,011
Liabilities:
Contingent consideration	33,567	45,172
Total Liabilities	85,298	70,833
Nasdaq Forwards
Assets:
Derivative asset	24,730	26,502
Rate lock commitments
Assets:
Derivative asset	50,170	32,035
Liabilities:
Derivative liability	1,114	12,124
Forward sale contracts
Assets:
Derivative asset	2,325	14,389
Liabilities:
Derivative liability	50,617	13,537
Level 1
Assets:
Marketable securities		36,795
Loans held for sale, at fair value	0	0
Total assets	0	36,795
Liabilities:
Contingent consideration	0	0
Total Liabilities	0	0
Level 1 | Nasdaq Forwards
Assets:
Derivative asset	0	0
Level 1 | Rate lock commitments
Assets:
Derivative asset	0	0
Liabilities:
Derivative liability	0	0
Level 1 | Forward sale contracts
Assets:
Derivative asset	0	0
Liabilities:
Derivative liability	0	0
Level 2
Assets:
Marketable securities		0
Loans held for sale, at fair value	1,089,429	215,290
Total assets	1,089,429	215,290
Liabilities:
Contingent consideration	0	0
Total Liabilities	0	0
Level 2 | Nasdaq Forwards
Assets:
Derivative asset	0	0
Level 2 | Rate lock commitments
Assets:
Derivative asset	0	0
Liabilities:
Derivative liability	0	0
Level 2 | Forward sale contracts
Assets:
Derivative asset	0	0
Liabilities:
Derivative liability	0	0
Level 3
Assets:
Marketable securities		0
Loans held for sale, at fair value	0	0
Total assets	77,225	72,926
Liabilities:
Contingent consideration	33,567	45,172
Total Liabilities	85,298	70,833
Level 3 | Nasdaq Forwards
Assets:
Derivative asset	24,730	26,502
Level 3 | Rate lock commitments
Assets:
Derivative asset	50,170	32,035
Liabilities:
Derivative liability	1,114	12,124
Level 3 | Forward sale contracts
Assets:
Derivative asset	2,325	14,389
Liabilities:
Derivative liability	$ 50,617	$ 13,537