Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Thousands, shares in Millions	9 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Loss Contingencies [Line Items]
Business acquisition, contingent cash consideration	$ 29,774	$ 28,099
Acquisitions from 2014 through 2019 [Member]
Loss Contingencies [Line Items]
Business acquisition, contingent cash consideration	$ 23,900
Business acquisition, contingent consideration limited partnership units	1.4
Construction Loans [Member]
Loss Contingencies [Line Items]
Total remaining draws on construction loans committed to fund	$ 627,000	$ 294,000