Summary of Significant Accounting Policies - Additional Information (Detail) $ in Thousands		3 Months Ended	9 Months Ended
	Jan. 02, 2018 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2019 USD ($) Practice_Groups	Sep. 30, 2018 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Number of practice groups | Practice_Groups			3
New accounting pronouncements or adoption of new standard resulted a (decrease) increase in net cash provided by investing activities			$ (24,691)	$ (39,267)
Accounting Standards Update 2016-02 [Member]
Summary Of Significant Accounting Policies [Line Items]
New accounting pronouncements or adoption of new standard resulted a (decrease) increase in net cash provided by investing activities				81,500
New accounting pronouncements or adoption of new standard resulted a (decrease) increase in cash, cash equivalents and restricted cash	$ 148,900			$ 67,400
Accounting Standards Update 2018-02 [Member] | Operating Expenses [Member]
Summary Of Significant Accounting Policies [Line Items]
New accounting pronouncement or change in accounting principle, effect of adoption, quantification		$ 6,000
Accounting Standards Update 2018-02 [Member] | Corporate General and Administrative Expenses [Member]
Summary Of Significant Accounting Policies [Line Items]
New accounting pronouncement or change in accounting principle, effect of adoption, quantification		700
Accounting Standards Update 2018-02 [Member] | Other Income, Net [Member]
Summary Of Significant Accounting Policies [Line Items]
New accounting pronouncement or change in accounting principle, effect of adoption, quantification		$ 6,700