Fair Value - Additional information (Detail) - USD ($)	Mar. 31, 2019	Dec. 31, 2018
Fair Value Measurements Nonrecurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	$ 0	$ 0
Liabilities measured at fair value	0	0
Fair Value Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	81,267,000	80,810,000
Liabilities measured at fair value	$ 0	$ 0