Employee Benefit Plans - Additional Information (Detail)	3 Months Ended		9 Months Ended				9 Months Ended			3 Months Ended	9 Months Ended
	Sep. 30, 2012 USD ($)	Sep. 30, 2011 USD ($)	Sep. 30, 2012 USD ($)	Sep. 30, 2011 USD ($)	Sep. 30, 2012 GBP (£)	Dec. 31, 2011 USD ($)	Sep. 30, 2012 U.S. Pension Plans [Member] USD ($)	Sep. 30, 2012 U.S. Pension Plans [Member] GBP (£)	Dec. 31, 2011 U.S. Pension Plans [Member] GBP (£)	Sep. 30, 2012 Payments From 2014 Through 2020 [Member] GBP (£)	Sep. 30, 2012 Payments From 2012 Through 2020 [Member] GBP (£)
Defined Benefit Plan Disclosure [Line Items]
Contribution related to the US pension plan			$ 700,000
Contribution to UK pension plan from previously established escrow account						3,687,000			2,300,000
Additional contribution to plan assets or escrow account										1,000,000	1,000,000
Amended amount from previous escrow arrangement					10,200,000
Aggregate amount in account security arrangement	16,500,000		16,500,000
Company's contribution to U.K. pension plans			1,577,000					1,000,000
Contributions to other non-U.S. pension plans	0		0
Total actuarial losses							1,935,000
Settlements loss							886,000
Net charges to OCI	$ (1,893,000)	$ (4,585,000)	$ (7,947,000)	$ (8,215,000)			$ 1,049,000