Benefit Plans - Weighted-Average Asset Allocation of Pension Plan Assets (Detail) - Pension	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Equities	100.00%	100.00%
Domestic equities
Defined Benefit Plan Disclosure [Line Items]
Equities	37.00%	34.00%
Foreign equities
Defined Benefit Plan Disclosure [Line Items]
Equities	11.00%	11.00%
Fixed income
Defined Benefit Plan Disclosure [Line Items]
Equities	50.00%	53.00%
Real estate
Defined Benefit Plan Disclosure [Line Items]
Equities	2.00%	2.00%
Cash
Defined Benefit Plan Disclosure [Line Items]
Equities	0.00%	0.00%