Summary of Significant Accounting Policies and Basis of Presentation (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Basis Of Presentation And Accounting Policies [Line Items]
Operating lease, right of use asset	$ 14,058,000
Operating lease, liabilities	13,510,000
Operating Lease Term of 12 Months or Less
Basis Of Presentation And Accounting Policies [Line Items]
Operating lease, right of use asset	0
Operating lease, liabilities	$ 0
Maximum
Basis Of Presentation And Accounting Policies [Line Items]
Operating lease, term of contract	12 months
Customer Relationship
Basis Of Presentation And Accounting Policies [Line Items]
Amortization of intangible assets		$ 2,697,000