New Accounting Standards - Additional Information (Detail) $ in Millions	Dec. 31, 2018 USD ($)
Minimum [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
ROU assets for operating leases	$ 32
Operating leases, liabilities	32
Maximum [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
ROU assets for operating leases	36
Operating leases, liabilities	$ 36