Pensions and Postretirement Benefits Other than Pensions - Assets of U.S and U.K Plans Using Fair Value Hierarchy (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Total	$ 1,146,430	$ 1,188,673	$ 1,112,314
Pension Benefits - Domestic [Member]
Defined Benefit Plan Disclosure [Line Items]
Cash & Cash Equivalents	724	770
Equity securities	495,933	451,893
Fixed income securities	339,857	405,162
Total	836,514	857,825
U K Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Cash & Cash Equivalents	917	935
Equity securities	65,391	67,280
Fixed income securities	214,762	234,775
Other investments	27,062	25,812
Total	308,132	328,802
Quoted Prices in Active Markets for Identical Assets Level (1) [Member] | Pension Benefits - Domestic [Member]
Defined Benefit Plan Disclosure [Line Items]
Cash & Cash Equivalents	724	770
Equity securities	149,894	153,129
Fixed income securities	133,420	137,693
Total	284,038	291,592
Quoted Prices in Active Markets for Identical Assets Level (1) [Member] | U K Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Cash & Cash Equivalents	917	935
Equity securities	65,391	67,280
Fixed income securities	214,762	234,775
Total	281,070	302,990
Significant Other Observable Inputs Level (2) [Member] | Pension Benefits - Domestic [Member]
Defined Benefit Plan Disclosure [Line Items]
Equity securities	346,039	298,764
Fixed income securities	206,437	267,469
Total	552,476	566,233
Significant Unobservable Inputs Level (3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Other investments	27,062	25,812	$ 13,915
Significant Unobservable Inputs Level (3) [Member] | U K Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Other investments	27,062	25,812
Total	$ 27,062	$ 25,812