Fair Value of Financial Assets and Liabilities - Changes in Level 3 Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Assets, Unobservable Input Reconciliation:
Opening Balance	$ 72,926	$ 92,528
Total realized and unrealized gains (losses) included in Net income (loss)	50,723	(4,693)
Issuances	0	0
Settlements	(46,424)	(14,909)
Closing Balance	77,225	72,926
Unrealized gains (losses) outstanding, at end of period	77,225	72,926
Liabilities, Unobservable Input Reconciliation:
Opening Balance	70,833	49,229
Total realized and unrealized (gains) losses included in Net income (loss)	39,468	27,948
Issuances	2,221	14,957
Settlements	(27,224)	(21,301)
Closing Balance	85,298	70,833
Unrealized (gains) losses outstanding, at end of period	51,815	27,948
Rate lock commitments
Assets, Unobservable Input Reconciliation:
Opening Balance	32,035	6,732
Total realized and unrealized gains (losses) included in Net income (loss)	50,170	32,035
Issuances	0	0
Settlements	(32,035)	(6,732)
Closing Balance	50,170	32,035
Unrealized gains (losses) outstanding, at end of period	50,170	32,035
Liabilities, Unobservable Input Reconciliation:
Opening Balance	12,124	7,470
Total realized and unrealized (gains) losses included in Net income (loss)	1,114	12,124
Issuances	0	0
Settlements	(12,124)	(7,470)
Closing Balance	1,114	12,124
Unrealized (gains) losses outstanding, at end of period	1,114	12,124
Contingent consideration
Liabilities, Unobservable Input Reconciliation:
Opening Balance	45,172	32,551
Total realized and unrealized (gains) losses included in Net income (loss)	(12,263)	2,287
Issuances	2,221	14,957
Settlements	(1,563)	(4,623)
Closing Balance	33,567	45,172
Unrealized (gains) losses outstanding, at end of period	84	2,287
Forward sale contracts
Assets, Unobservable Input Reconciliation:
Opening Balance	14,389	8,177
Total realized and unrealized gains (losses) included in Net income (loss)	2,325	14,389
Issuances	0	0
Settlements	(14,389)	(8,177)
Closing Balance	2,325	14,389
Unrealized gains (losses) outstanding, at end of period	2,325	14,389
Liabilities, Unobservable Input Reconciliation:
Opening Balance	13,537	9,208
Total realized and unrealized (gains) losses included in Net income (loss)	50,617	13,537
Issuances	0	0
Settlements	(13,537)	(9,208)
Closing Balance	50,617	13,537
Unrealized (gains) losses outstanding, at end of period	50,617	13,537
Nasdaq Forwards
Assets, Unobservable Input Reconciliation:
Opening Balance	26,502	77,619
Total realized and unrealized gains (losses) included in Net income (loss)	(1,772)	(51,117)
Issuances	0	0
Settlements	0	0
Closing Balance	24,730	26,502
Unrealized gains (losses) outstanding, at end of period	$ 24,730	$ 26,502