Fair Value of Financial Assets and Liabilities - Fair Value Hierarchy of Financial Assets and Liabilities under U.S. GAAP Guidance (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Nov. 30, 2019
Assets:
Marketable securities	$ 0	$ 36,795	$ 98,600
Derivative contract, Assets	106,656	72,926
Loans held for sale, at fair value	739,383	215,290
Total assets	846,039	325,011
Liabilities:
Accounts payable, accrued expenses and other liabilities—contingent consideration	33,337	45,172
Derivative contract, Liabilities	77,909	25,661
Total Liabilities	111,246	70,833
Nasdaq Forwards
Assets:
Derivative contract, Assets	47,675	26,502
Rate lock commitments
Assets:
Derivative contract, Assets	58,752	32,035
Liabilities:
Derivative contract, Liabilities		12,124
Forward sale contracts
Assets:
Derivative contract, Assets	229	14,389
Liabilities:
Derivative contract, Liabilities	77,909	13,537
Level 1
Assets:
Loans held for sale, at fair value	0	0
Total assets	0	36,795
Liabilities:
Accounts payable, accrued expenses and other liabilities—contingent consideration	0	0
Total Liabilities	0	0
Level 1 | Nasdaq Forwards
Assets:
Derivative contract, Assets	0	0
Level 1 | Rate lock commitments
Assets:
Derivative contract, Assets	0	0
Liabilities:
Derivative contract, Liabilities		0
Level 1 | Forward sale contracts
Assets:
Derivative contract, Assets	0	0
Liabilities:
Derivative contract, Liabilities	0	0
Level 2
Assets:
Marketable securities		0
Loans held for sale, at fair value	739,383	215,290
Total assets	739,383	215,290
Liabilities:
Accounts payable, accrued expenses and other liabilities—contingent consideration	0	0
Total Liabilities	0	0
Level 2 | Nasdaq Forwards
Assets:
Derivative contract, Assets	0	0
Level 2 | Rate lock commitments
Assets:
Derivative contract, Assets	0	0
Liabilities:
Derivative contract, Liabilities		0
Level 2 | Forward sale contracts
Assets:
Derivative contract, Assets	0	0
Liabilities:
Derivative contract, Liabilities	0	0
Level 3
Assets:
Marketable securities		0
Loans held for sale, at fair value	0	0
Total assets	106,656	72,926
Liabilities:
Accounts payable, accrued expenses and other liabilities—contingent consideration	33,337	45,172
Total Liabilities	111,246	70,833
Level 3 | Nasdaq Forwards
Assets:
Derivative contract, Assets	47,675	26,502
Level 3 | Rate lock commitments
Assets:
Derivative contract, Assets	58,752	32,035
Liabilities:
Derivative contract, Liabilities	0	12,124
Level 3 | Forward sale contracts
Assets:
Derivative contract, Assets	229	14,389
Liabilities:
Derivative contract, Liabilities	$ 77,909	$ 13,537