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, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Total	$ 160,423	$ 134,198	$ 147,908
Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	115,591	95,478
Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	44,832	38,720
Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	7,261	4,935
Cash and Cash Equivalents [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	7,261	4,935
Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	97,250	84,229
Equity Securities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	97,250	84,229
U.S. Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	50,319	34,751
U.S. Equities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	50,319	34,751
Non-U.S. Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	19,697	27,415
Non-U.S. Equities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	19,697	27,415
Employer Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	27,234	22,063
Employer Securities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	27,234	22,063
Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	55,912	45,034
Fixed Income Securities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	11,080	6,314
Fixed Income Securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	44,832	38,720
U.S. Corporate Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	36,242	29,659
U.S. Corporate Bonds [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	36,242	29,659
U.S. Government and Agency Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	11,080	9,453
U.S. Government and Agency Bonds [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	11,080	6,314
U.S. Government and Agency Bonds [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total		3,139
Other Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	8,590	5,922
Other Bonds [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	$ 8,590	$ 5,922