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, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	$ 73,386	$ 80,423
Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	623	264
U.S. large value
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	4,815	5,499
U.S. large growth
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	5,270	5,792
International blend
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	9,134	10,734
International growth
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	3,093
Emerging markets
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	0	3,613
Balanced
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	17,952	21,895
Government bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	10,240	9,806
Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	11,297	12,667
U.S. property
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	10,962	10,153
Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	13,801	15,168
Level 1 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	623	264
Level 1 | U.S. large value
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	4,815	5,499
Level 1 | U.S. large growth
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	5,270	5,792
Level 1 | International growth
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	3,093
Level 1 | Emerging markets
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	0	3,613
Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	48,623	55,102
Level 2 | International blend
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	9,134	10,734
Level 2 | Balanced
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	17,952	21,895
Level 2 | Government bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	10,240	9,806
Level 2 | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	11,297	12,667
Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	10,962	10,153	$ 9,409
Level 3 | U.S. property
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	$ 10,962	$ 10,153