Defined Contribution Plans, Pension and Other Post-Retirement Benefit Plans - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Defined Benefit Plan Disclosure [Line Items]
Recognized expense associated with defined contribution plans	$ 2,200,000	$ 1,000,000	$ 600,000
Expected contribution to pension plans and post-retirement benefit plans	2,400,000
Maturity period of investments	90 days
Annual rate of increase in per capital cost for 2012	7.50%
Rate of assumed decrease in per capital cost through 2017	5.00%
Defined Contribution Pension
Defined Benefit Plan Disclosure [Line Items]
Estimated actuarial loss for defined benefit plans	400,000
Other Post-Retirement Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Estimated actuarial loss for defined benefit plans	$ 358,000	$ (51,000)