Leases - Schedule of Operating Lease ROU Assets and Operating Lease Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
Leases [Abstract]
Operating Lease ROU Assets	$ 21,628	$ 22,000	$ 0
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:OtherAssets
Operating Lease Liabilities	$ 40,518	$ 40,300
Operating Lease, Liability, Statement of Financial Position [Extensible List]	us-gaap:AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent