Pension and Post-Retirement Benefits - Amounts in Accumulated Other Comprehensive Income Expected to be Recognized as Components of Net Periodic Benefit Cost (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Pension Plans, Postretirement and Other Employee Benefits
Defined Benefit Plan, Accumulated Other Comprehensive Income Net Gains (Losses), after Tax	$ 14,100	$ 17,700
Net actuarial loss	1,294
Prior service cost	333
Total	1,627
Defined Benefit Plan, Accumulated Other Comprehensive Income Net Prior Service Cost (Credit), after Tax	1,800	$ 1,600
Pension Benefits
Pension Plans, Postretirement and Other Employee Benefits
Net actuarial loss	1,294
Prior service cost	333
Total	1,627
Post-retirement Benefits
Pension Plans, Postretirement and Other Employee Benefits
Net actuarial loss	0
Prior service cost	0
Total	$ 0