Pension and Post-Retirement Benefits - Fair Value of Pension Plan Assets, by Asset Category (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Cash and Cash Equivalents
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	$ 1,635	$ 1,897
Diversified Emerging Markets
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	6,890	8,136
Foreign Large Blend
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	13,111	13,216
Large-Cap Blend
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	16,855	19,662
Long-Term Bonds
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets		36,782
Mid-Cap Blend
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	7,769	6,293
Real Estate
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	4,369	4,844
Corporate Notes And Bonds [Member]
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	22,559
Government Agency [Member]
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	607
US Treasury Securities [Member]
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	5,384
Collateralized Mortgage Backed Securities [Member]
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	3,111
Asset-backed Securities [Member]
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	2,375
Insurance Policies
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	51	67
Net Asset
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	84,716	90,897
Level 1 | Cash and Cash Equivalents
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	0	1,897
Level 1 | Diversified Emerging Markets
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	6,890	8,136
Level 1 | Foreign Large Blend
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	13,111	13,216
Level 1 | Large-Cap Blend
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	16,855	19,662
Level 1 | Long-Term Bonds
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets		36,782
Level 1 | Mid-Cap Blend
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	7,769	6,293
Level 1 | Real Estate
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	4,369	4,844
Level 1 | Corporate Notes And Bonds [Member]
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	22,559
Level 1 | Government Agency [Member]
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	607
Level 1 | US Treasury Securities [Member]
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	5,384
Level 1 | Collateralized Mortgage Backed Securities [Member]
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	0
Level 1 | Asset-backed Securities [Member]
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	0
Level 1 | Insurance Policies
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	0	0
Level 1 | Net Asset
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	77,544	90,830
Level 2 | Cash and Cash Equivalents
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	1,635	0
Level 2 | Diversified Emerging Markets
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	0	0
Level 2 | Foreign Large Blend
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	0	0
Level 2 | Large-Cap Blend
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	0	0
Level 2 | Long-Term Bonds
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets		0
Level 2 | Mid-Cap Blend
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	0	0
Level 2 | Real Estate
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	0	0
Level 2 | Corporate Notes And Bonds [Member]
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	0
Level 2 | Government Agency [Member]
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	0
Level 2 | US Treasury Securities [Member]
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	0
Level 2 | Collateralized Mortgage Backed Securities [Member]
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	3,111
Level 2 | Asset-backed Securities [Member]
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	2,375
Level 2 | Insurance Policies
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	0	0
Level 2 | Net Asset
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	7,121	0
Level 3 | Cash and Cash Equivalents
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	0	0
Level 3 | Diversified Emerging Markets
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	0	0
Level 3 | Foreign Large Blend
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	0	0
Level 3 | Large-Cap Blend
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	0	0
Level 3 | Long-Term Bonds
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets		0
Level 3 | Mid-Cap Blend
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	0	0
Level 3 | Real Estate
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	0	0
Level 3 | Corporate Notes And Bonds [Member]
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	0
Level 3 | Government Agency [Member]
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	0
Level 3 | US Treasury Securities [Member]
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	0
Level 3 | Collateralized Mortgage Backed Securities [Member]
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	0
Level 3 | Asset-backed Securities [Member]
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	0
Level 3 | Insurance Policies
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	51	67
Level 3 | Net Asset
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	$ 51	$ 67