Benefit Plans - Weighted-Average Asset Allocation of Pension Plan Assets (Detail)	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Equities	100.00%	100.00%
Domestic equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Equities	36.00%	41.00%
Foreign equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Equities	11.00%	12.00%
Fixed income [Member]
Defined Benefit Plan Disclosure [Line Items]
Equities	51.00%	45.00%
Real estate [Member]
Defined Benefit Plan Disclosure [Line Items]
Equities	2.00%	2.00%
Cash [Member]
Defined Benefit Plan Disclosure [Line Items]
Equities	0.00%	0.00%