Defined Contribution Plans, Pension and Other Post-Retirement Benefit Plans - Fair Values of Pension Plan Assets by Asset Category and by Level (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	$ 69,470	$ 69,876
Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	174	551
U.S. large value
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	4,800	4,222
U.S. large growth
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	4,805	3,961
International blend
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	7,954	7,874
Emerging Markets
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	2,464	2,429
Balanced
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	18,486	20,528
Government Bond Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	8,402	4,298
Corporate Bond Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	12,976	17,368
U.S. property
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	9,409	8,645
Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	12,243	11,163
Level 1 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	174	551
Level 1 | U.S. large value
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	4,800	4,222
Level 1 | U.S. large growth
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	4,805	3,961
Level 1 | Emerging Markets
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	2,464	2,429
Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	47,818	50,068
Level 2 | International blend
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	7,954	7,874
Level 2 | Balanced
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	18,486	20,528
Level 2 | Government Bond Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	8,402	4,298
Level 2 | Corporate Bond Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	12,976	17,368
Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	9,409	8,645	$ 7,957
Level 3 | U.S. property
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	$ 9,409	$ 8,645