Schedule of Fair Value of Pensions Plan Assets by Asset Category (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Schedule of Pension Plan Assets by Fair Value [Line Items]
Total	$ 302,899	$ 339,580
Fixed Income Securities | Corporate Debt Securities
Schedule of Pension Plan Assets by Fair Value [Line Items]
Total	157,263	172,401
Fixed Income Securities | US Government Debt Securities
Schedule of Pension Plan Assets by Fair Value [Line Items]
Total	82,674	102,027
Fixed Income Securities | U.K. Government Securities
Schedule of Pension Plan Assets by Fair Value [Line Items]
Total	8,593	7,553
Fixed Income Securities | Asset-backed Securities
Schedule of Pension Plan Assets by Fair Value [Line Items]
Total	2,042	4,604
U.S. Equity (Large Cap)
Schedule of Pension Plan Assets by Fair Value [Line Items]
Total	23,832	27,725
International Equity
Schedule of Pension Plan Assets by Fair Value [Line Items]
Total	23,990	21,285
Guarantee Annuity Contract
Schedule of Pension Plan Assets by Fair Value [Line Items]
Total	3,108	2,863
Other
Schedule of Pension Plan Assets by Fair Value [Line Items]
Total	839	711
Cash and Cash Equivalents
Schedule of Pension Plan Assets by Fair Value [Line Items]
Total	558	411
Quoted Prices in Active Markets for Identical Instruments (Level 1)
Schedule of Pension Plan Assets by Fair Value [Line Items]
Total	23,712	5,136
Quoted Prices in Active Markets for Identical Instruments (Level 1) | Fixed Income Securities | US Government Debt Securities
Schedule of Pension Plan Assets by Fair Value [Line Items]
Total	23,712	5,136
Significant Other Observable Inputs (Level 2)
Schedule of Pension Plan Assets by Fair Value [Line Items]
Total	279,187	334,444
Significant Other Observable Inputs (Level 2) | Fixed Income Securities | Corporate Debt Securities
Schedule of Pension Plan Assets by Fair Value [Line Items]
Total	157,263	172,401
Significant Other Observable Inputs (Level 2) | Fixed Income Securities | US Government Debt Securities
Schedule of Pension Plan Assets by Fair Value [Line Items]
Total	58,962	96,891
Significant Other Observable Inputs (Level 2) | Fixed Income Securities | U.K. Government Securities
Schedule of Pension Plan Assets by Fair Value [Line Items]
Total	8,593	7,553
Significant Other Observable Inputs (Level 2) | Fixed Income Securities | Asset-backed Securities
Schedule of Pension Plan Assets by Fair Value [Line Items]
Total	2,042	4,604
Significant Other Observable Inputs (Level 2) | U.S. Equity (Large Cap)
Schedule of Pension Plan Assets by Fair Value [Line Items]
Total	23,832	27,725
Significant Other Observable Inputs (Level 2) | International Equity
Schedule of Pension Plan Assets by Fair Value [Line Items]
Total	23,990	21,285
Significant Other Observable Inputs (Level 2) | Guarantee Annuity Contract
Schedule of Pension Plan Assets by Fair Value [Line Items]
Total	3,108	2,863
Significant Other Observable Inputs (Level 2) | Other
Schedule of Pension Plan Assets by Fair Value [Line Items]
Total	839	711
Significant Other Observable Inputs (Level 2) | Cash and Cash Equivalents
Schedule of Pension Plan Assets by Fair Value [Line Items]
Total	$ 558	$ 411