Employee and Retiree Benefit Plans - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Pension and Other Postretirement Benefits Disclosure [Line Items]
Future annual rate of increase in cost of health care for 2012 to measure postretirement benefit obligations	7.40%
Ultimate rate of health care cost in 2020 and thereafter	5.00%
Provisions of the March 2010 Health Care Reform	In March 2010, the United States Congress enacted a health care reform law. Along with other provisions, the law (a) eliminates the tax free status of federal subsidies to companies with qualified retiree prescription drug plans that are actuarially equivalent to Medicare Part D plans beginning in 2013; (b) imposes a 40% excise tax on high-cost health plans as defined in the law beginning in 2018; (c) eliminates lifetime or annual coverage limits and required coverage for preventative health services beginning in September 2010; and (d) imposed a fee of $2 (subsequently adjusted for inflation) for each person covered by a health insurance policy beginning in September 2010.
Excise tax rate imposed on high-cost health plans beginning 2018	40.00%
Government imposed fee for each person covered by health insurance policy	$ 2
Equity securities minimum market capitalization	100,000,000
Weighted average expected return on plan asset	6.20%
Amounts charged to expense for U.S. and U.K. plans	12,594,000	10,725,000	11,467,000
Defined benefit plan, percentage of employer's matching contribution	6.00%	6.00%	6.00%
Foreign Other Postretirement Benefit Plans
Pension and Other Postretirement Benefits Disclosure [Line Items]
Contributions to benefit plans	46,000
Expected benefit plan contributions to be made during next year	40,000
Funded Retirement Plan
Pension and Other Postretirement Benefits Disclosure [Line Items]
Weighted average expected return on plan asset	6.86%
Domestic postretirement benefits plan
Pension and Other Postretirement Benefits Disclosure [Line Items]
Contributions to benefit plans	4,614,000
Expected benefit plan contributions to be made during next year	5,607,000
Domestic defined benefit pension plans
Pension and Other Postretirement Benefits Disclosure [Line Items]
Contributions to benefit plans	27,456,000
Expected benefit plan contributions to be made during next year	26,659,000
Foreign Defined Benefit Pension Plans
Pension and Other Postretirement Benefits Disclosure [Line Items]
Contributions to benefit plans	14,751,000
Expected benefit plan contributions to be made during next year	$ 16,192,000
Maximum
Pension and Other Postretirement Benefits Disclosure [Line Items]
Investment Manager's portfolio to be held in equity securities of any one issuer	10.00%
United Kingdom
Pension and Other Postretirement Benefits Disclosure [Line Items]
Percentage fixed income allocation	95.00%
United Kingdom | Foreign Other Postretirement Benefit Plans
Pension and Other Postretirement Benefits Disclosure [Line Items]
Description of equity and fixed income securities allocation	Approximately one-half of the equity allocation is to be invested in U.K. securities and the reminder split between North American, European, Japanese and other Pacific Basin securities. A minimum of 95% of the fixed income allocation is to be invested in U.K. securities with up to 5% in international or high yield bonds.
Asset performance compared to a benchmark return, percent targeted to outperform the benchmark over three years	0.75%
United Kingdom | Maximum
Pension and Other Postretirement Benefits Disclosure [Line Items]
Maximum percentage of income investment in securities	5.00%
Equity securities
Pension and Other Postretirement Benefits Disclosure [Line Items]
Target allocations of plan assets, minimum	40.00%
Target allocations of plan assets, maximum	70.00%
Basis used to determine expected return on plan asset, percentage of expected return (expense)	8.20%
Equity securities | United Kingdom | Foreign Other Postretirement Benefit Plans
Pension and Other Postretirement Benefits Disclosure [Line Items]
Target allocations of plan assets, minimum	27.00%
Target allocations of plan assets, maximum	98.00%
Target allocations of plan assets	60.00%
Equity securities | Canada | Foreign Other Postretirement Benefit Plans
Pension and Other Postretirement Benefits Disclosure [Line Items]
Target allocations of plan assets, minimum	50.00%
Target allocations of plan assets, maximum	70.00%
Target allocations of plan assets	65.00%
Fixed Income Securities
Pension and Other Postretirement Benefits Disclosure [Line Items]
Target allocations of plan assets, minimum	30.00%
Target allocations of plan assets, maximum	60.00%
Fixed income portfolio, maximum average maturity years	11
Weighted average expected return on plan asset	3.70%
Basis used to determine expected return on plan asset, percentage of expected return (expense)	0.39%
Fixed Income Securities | United Kingdom | Foreign Other Postretirement Benefit Plans
Pension and Other Postretirement Benefits Disclosure [Line Items]
Target allocations of plan assets, minimum	25.00%
Target allocations of plan assets, maximum	60.00%
Target allocations of plan assets	40.00%
Fixed Income Securities | Canada | Foreign Other Postretirement Benefit Plans
Pension and Other Postretirement Benefits Disclosure [Line Items]
Target allocations of plan assets, minimum	25.00%
Target allocations of plan assets, maximum	50.00%
Target allocations of plan assets	30.00%
US long/short equity fund
Pension and Other Postretirement Benefits Disclosure [Line Items]
Target allocations of plan assets, minimum	0.00%
Target allocations of plan assets, maximum	15.00%
Cash equivalents
Pension and Other Postretirement Benefits Disclosure [Line Items]
Target allocations of plan assets, minimum	0.00%
Target allocations of plan assets, maximum	15.00%
Cash equivalents | United Kingdom | Foreign Other Postretirement Benefit Plans
Pension and Other Postretirement Benefits Disclosure [Line Items]
Target allocations of plan assets, maximum	5.00%
Cash equivalents | Canada | Foreign Other Postretirement Benefit Plans
Pension and Other Postretirement Benefits Disclosure [Line Items]
Target allocations of plan assets, minimum	0.00%
Target allocations of plan assets, maximum	20.00%
Target allocations of plan assets	5.00%
Commingled trust fund | Minimum | Domestic postretirement benefits plan
Pension and Other Postretirement Benefits Disclosure [Line Items]
Domestic plan, commingled trusts waiting periods for withdrawals (in days)	6 days
Commingled trust fund | Maximum | Domestic postretirement benefits plan
Pension and Other Postretirement Benefits Disclosure [Line Items]
Domestic plan, commingled trusts waiting periods for withdrawals (in days)	30 days