Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Loss Contingencies [Line Items]
Total remaining draws on construction loans committed to fund	$ 437,000		$ 244,000
Rent expense	10,200	$ 9,800
Business acquisition, contingent cash consideration	15,971		$ 17,207
Long-term Debt Payable to Related Parties [Member]
Loss Contingencies [Line Items]
Business acquisition, contingent cash consideration	$ 12,400