Expected Future Benefit Payments of Pension and Other Post-Retirement Benefit Plans (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012
Pension Plans, Defined Benefit
Schedule of Pension and Other Postretirement Benefits Expected Benefit Payments [Line Items]
2013	$ 3,123
2014	3,357
2015	3,573
2016	3,807
2017	4,095
2018 to 2022	25,217
Other Post-Retirement Benefit Plans
Schedule of Pension and Other Postretirement Benefits Expected Benefit Payments [Line Items]
2013	175
2014	153
2015	106
2016	95
2017	95
2018 to 2022	$ 251