Fair Value of Financial Assets and Liabilities - Changes in Level 3 Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - Level 3 [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Accounts Payable Accrued and Other Liabilities [Member] | Contingent Consideration [Member]
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Opening Balance, Liabilities	$ 69,003	$ 72,854	$ 66,004	$ 75,061
Total realized and unrealized gains (losses) included in Net income (loss), Liabilities	(1,959)	16,571	(5,946)	15,258
Unrealized gains (losses) included in Other comprehensive income (loss), Liabilities	(884)	53	(2,043)	131
Issuances, Liabilities	1,262	5,631	9,624	7,042
Settlements, Liabilities	(1,702)	(1,299)	(12,211)	(6,152)
Closing Balance, Liabilities	71,406	60,562	71,406	60,562
Unrealized gains (losses) for Level 3 Liabilities Outstanding	(2,844)	(643)	(7,990)	(1,878)
Rate Lock Commitments And Forwards, Net [Member]
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Opening Balance, Assets	10,566	5,115	10,254	6,300
Total realized and unrealized gains (losses) included in Net income (loss), Assets	10,070	5,182	10,070	5,182
Settlements, Assets	(10,566)	(5,115)	(10,254)	(6,300)
Closing Balance, Assets	10,070	5,182	10,070	5,182
Unrealized gains (losses) for Level 3 Assets Outstanding	$ 10,070	$ 5,182	$ 10,070	$ 5,182