Employee Pension Benefits - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Defined Benefit Plan Disclosure [Line Items]
Service cost included in net periodic pension benefit			$ 0
Esi Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Contributions to the pension plans	0	0	0	0
Esi Excess Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Contributions to the pension plans	$ 0	$ 0	$ 0	$ 0