Other Comprehensive Income - Amounts Reclassified Out of Each Component of Accumulated Other Comprehensive Loss (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Statement Of Income And Comprehensive Income [Abstract]
Unrealized gains and losses on available-for-sale securities, Net gain on sale of securities	$ 80		$ 138
Unrealized gains and losses on available-for-sale securities, Total before tax	80		138	40
Unrealized gains and losses on available-for-sale securities, Tax effect	(27)		(47)	(14)
Unrealized gains and losses on available-for-sale securities, Net of tax	53		91
Amortization of defined benefit pension items, Actuarial gains/(losses), Salaries, wages and benefits	(180)		(518)
Amortization of defined benefit pension items, Total before tax	(180)	(90)	(518)	(270)
Amortization of defined benefit pension items, Tax effect	61	31	176	92
Amortization of defined benefit pension items, Net of tax	(119)		(342)
Total reclassifications for the period, Net of tax	$ (66)		$ (251)