Reclassifications out of Accumulated Other Comprehensive Income (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Accumulated Other Comprehensive Income (Loss) [Line Items]
Unrealized gains and losses on available for Sale securities, Before tax amount	$ 211	$ 272
Unrealized gains and losses on available for Sale securities, Tax (expense)/benefit	(202)	30
Amortization of prior service cost included in net periodic pension cost, Before tax amount	(14)	(5)
Direct Cost
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amortization of prior service cost included in net periodic pension cost, Before tax amount	(14)	(5)
Amortization of prior service cost included in net periodic pension cost, Tax (expense)/benefit	5	1
Amortization of prior service cost included in net periodic pension cost, Net of tax	(9)	(4)
Other Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Unrealized gains and losses on available for Sale securities, Before tax amount	612	(95)
Unrealized gains and losses on available for Sale securities, Tax (expense)/benefit	(202)	30
Unrealized gains and losses on available for Sale securities, Net of tax	$ 410	$ (65)