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	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Assets, Unobservable Input Reconciliation:
Opening Balance	$ 72,926	$ 92,528
Total realized and unrealized gains (losses) included in Net income	80,154	(4,693)
Issuances	0	0
Settlements	(46,424)	(14,909)
Closing Balance	106,656	72,926
Unrealized gains (losses) outstanding, at end of period	106,656	72,926
Liabilities, Unobservable Input Reconciliation:
Opening Balance	70,833	49,229
Total realized and unrealized (gains) losses included in Net income	65,796	27,948
Issuances	2,221	14,957
Settlements	(27,604)	(21,301)
Closing Balance	111,246	70,833
Unrealized gains (losses) outstanding, at end of period	78,609	27,948
Contingent consideration
Liabilities, Unobservable Input Reconciliation:
Opening Balance	45,172	32,551
Total realized and unrealized (gains) losses included in Net income	(12,113)	2,287
Issuances	2,221	14,957
Settlements	(1,943)	(4,623)
Closing Balance	33,337	45,172
Unrealized gains (losses) outstanding, at end of period	700	2,287
Rate lock commitments
Assets, Unobservable Input Reconciliation:
Opening Balance	32,035	6,732
Total realized and unrealized gains (losses) included in Net income	58,752	32,035
Issuances	0	0
Settlements	(32,035)	(6,732)
Closing Balance	58,752	32,035
Unrealized gains (losses) outstanding, at end of period	58,752	32,035
Liabilities, Unobservable Input Reconciliation:
Opening Balance	12,124	7,470
Total realized and unrealized (gains) losses included in Net income	0	12,124
Issuances		0
Settlements	(12,124)	(7,470)
Closing Balance	0	12,124
Unrealized gains (losses) outstanding, at end of period	0	12,124
Forward sale contracts
Assets, Unobservable Input Reconciliation:
Opening Balance	14,389	8,177
Total realized and unrealized gains (losses) included in Net income	229	14,389
Issuances	0	0
Settlements	(14,389)	(8,177)
Closing Balance	229	14,389
Unrealized gains (losses) outstanding, at end of period	229	14,389
Liabilities, Unobservable Input Reconciliation:
Opening Balance	13,537	9,208
Total realized and unrealized (gains) losses included in Net income	77,909	13,537
Issuances	0	0
Settlements	(13,537)	(9,208)
Closing Balance	77,909	13,537
Unrealized gains (losses) outstanding, at end of period	77,909	13,537
Nasdaq Forwards
Assets, Unobservable Input Reconciliation:
Opening Balance	26,502	77,619
Total realized and unrealized gains (losses) included in Net income	21,173	(51,117)
Issuances	0	0
Settlements	0	0
Closing Balance	47,675	26,502
Unrealized gains (losses) outstanding, at end of period	$ 47,675	$ 26,502