Recent Accounting Developments - Additional Information (Detail) - USD ($)	Sep. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Increase in right of use asset due to adopting new standard	$ 4,600,000
Other assets	30,305,000		$ 23,060,000
Increase in lease liability due to adopting new standard	$ 4,936,000
ASU 2016-02 [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Increase in right of use asset due to adopting new standard		$ 5,200,000
Other assets		300,000
Increase in lease liability due to adopting new standard		$ 5,500,000