Employee Benefits - Narrative (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2016 USD ($)
Minimum
Defined Benefit Plan Disclosure [Line Items]
Estimated settlement charge of individuals elect the option to receive a lump sum pension payment or annuity	$ 90.0
Percentage of individuals elect the option to receive a lump sum pension payment or annuity	30.00%
Maximum
Defined Benefit Plan Disclosure [Line Items]
Estimated settlement charge of individuals elect the option to receive a lump sum pension payment or annuity	$ 100.0
Percentage of individuals elect the option to receive a lump sum pension payment or annuity	35.00%