Postretirement Benefit Plans - Company's Asset Allocations for its U.S. Pension Plans by Asset Category (Detail) - United States [Member] - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Total	$ 134,198	$ 147,908	$ 137,092
Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	95,478	109,979
Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	38,720	37,929
Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	4,935	4,903
Cash and Cash Equivalents [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	4,935	4,903
U.S. Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	34,751	37,753
U.S. Equities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	34,751	37,753
Non-U.S. Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	27,415	31,628
Non-U.S. Equities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	27,415	31,581
Non-U.S. Equities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total		47
Employer Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	22,063	30,197
Employer Securities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	22,063	30,197
Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	84,229	99,578
Equities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	84,229	99,531
Equities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total		47
U.S. Corporate Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	29,659	28,744
U.S. Corporate Bonds [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	29,659	28,744
U.S. Government and Agency Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	9,453	6,590
U.S. Government and Agency Bonds [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	6,314	5,545
U.S. Government and Agency Bonds [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	3,139	1,045
Other Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	5,922	8,093
Other Bonds [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	5,922	8,093
Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	45,034	43,427
Debt Securities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	6,314	5,545
Debt Securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	$ 38,720	$ 37,882