Employee Benefits Plans (Detail) - Net Periodic Benefit Cost Not yet Recognized (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012
Supplemental Employee Retirement Plans, Defined Benefit [Member]
Net loss	$ 773
Prior service credit
Total	773
Other Postretirement Benefit Plans, Defined Benefit [Member]
Net loss	118
Prior service credit	(414)
Total	$ (296)