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, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Total	$ 121,835	$ 126,369	$ 133,264
Municipal Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total		3,352
Commodities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	1,481	2,023
Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	76,708	76,896
Level 1 [Member] | Commodities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	1,481	2,023
Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	45,127	49,473
Level 2 [Member] | Municipal Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total		3,352
Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	1,989	1,963
Cash and Cash Equivalents [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	1,989	1,963
U.S. Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	33,076	34,885
U.S. Equities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	33,076	34,885
Non-U.S. Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	10,630	12,478
Non-U.S. Equities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	10,630	12,478
Employer Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	24,792	21,575
Employer Securities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	24,792	21,575
Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	68,498	68,938
Equities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	68,498	68,938
U.S. Corporate Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	26,389	27,676
U.S. Corporate Bonds [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	26,389	27,676
U.S. Government and Agency Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	9,736	10,677
U.S. Government and Agency Bonds [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	365	350
U.S. Government and Agency Bonds [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	9,371	10,327
Other Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	7,378	6,155
Other Bonds [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	7,378	6,155
Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	43,503	47,860
Debt Securities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	365	350
Debt Securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	43,138	47,510
Real Estate Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	5,222	5,585
Real Estate Fund [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	5,222	5,585
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	7,845	7,608
Mutual Funds | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	$ 7,845	$ 7,608