Leases, Commitments and Contingencies - Operating Leases - Additional Information (Detail) $ in Millions						1 Months Ended					3 Months Ended		6 Months Ended
	Jun. 30, 2019 ft²	Feb. 28, 2019 ft²	Oct. 02, 2018 ft²	Sep. 30, 2018 ft²	Aug. 01, 2018 ft²	Mar. 31, 2019 ft²	Dec. 31, 2018 ft²	Oct. 31, 2018 ft²	May 31, 2018 ft²	Apr. 30, 2018 ft²	Jun. 30, 2019 USD ($)	Mar. 31, 2018 ft²	Jun. 30, 2019 USD ($)
Commitments And Contingencies [Line Items]
Operating lease option to extend													true
Operating lease renewal term	5 years										5 years		5 years
Expenses for short term lease | $											$ 0.1		$ 0.3
Operating Lease One [Member]
Commitments And Contingencies [Line Items]
Office space rent under operating lease	63,017	58,442		54,943		63,017		58,442
Lease expire date	Aug. 31, 2024					Aug. 31, 2024		Aug. 31, 2024
Increased office space rent						4,575		3,499
Operating Lease Two [Member]
Commitments And Contingencies [Line Items]
Office space rent under operating lease										40,419		19,805
Lease expire date										Aug. 31, 2024		Feb. 28, 2022	Aug. 31, 2024
Increased office space rent			7,133		13,481					20,614
Operating Lease Three [Member]
Commitments And Contingencies [Line Items]
Office space rent under operating lease									15,525
Lease expire date									Nov. 30, 2024
Operating Lease Five [Member]
Commitments And Contingencies [Line Items]
Office space rent under operating lease							15,975
Lease expire date							Feb. 28, 2024
Minimum [Member]
Commitments And Contingencies [Line Items]
Operating lease remaining lease terms													1 year
Maximum [Member]
Commitments And Contingencies [Line Items]
Operating lease remaining lease terms													6 years