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, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Total	$ 137,092	$ 121,835	$ 126,369
Commodities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	2,523	1,481
Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	99,872	76,708
Level 1 [Member] | Commodities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	2,523	1,481
Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	37,220	45,127
Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	3,908	1,989
Cash and Cash Equivalents [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	3,633
Cash and Cash Equivalents [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	275	1,989
U.S. Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	29,390	33,076
U.S. Equities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	29,390	33,076
Non-U.S. Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	14,637	10,630
Non-U.S. Equities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	14,637	10,630
Employer Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	36,018	24,792
Employer Securities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	36,018	24,792
Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	80,045	68,498
Equities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	80,045	68,498
U.S. Corporate Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	28,278	26,389
U.S. Corporate Bonds [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	28,278	26,389
U.S. Government and Agency Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	9,280	9,736
U.S. Government and Agency Bonds [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	8,309	365
U.S. Government and Agency Bonds [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	971	9,371
Other Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	7,696	7,378
Other Bonds [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	7,696	7,378
Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	45,254	43,503
Debt Securities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	8,309	365
Debt Securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	36,945	43,138
Real Estate Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	5,362	5,222
Real Estate Fund [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	5,362	5,222
Other
Defined Benefit Plan Disclosure [Line Items]
Total		1,142
Other | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total		1,142
Mutual Funds
Defined Benefit Plan Disclosure [Line Items]
Total	7,885	7,845
Mutual Funds | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	$ 7,885	$ 7,845