Other Comprehensive Income - Changes in Each Component of Accumulated Other Comprehensive Loss, Net of Tax (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ (4,247)	$ (1,647)
Other comprehensive loss before reclassifications	1,318	(412)
Amounts reclassified from accumulated other comprehensive loss	25	93
Net current-period other comprehensive income (loss)	1,343	(319)
Ending balance	(2,904)	(1,966)
Unrealized Gains and Losses on Available-for-Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	341	5,849
Other comprehensive loss before reclassifications	1,318	(412)
Amounts reclassified from accumulated other comprehensive loss	(3)	(11)
Net current-period other comprehensive income (loss)	1,315	(423)
Ending balance	1,656	5,426
Defined Benefit Pension Items [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(4,588)	(7,496)
Other comprehensive loss before reclassifications
Amounts reclassified from accumulated other comprehensive loss	28	104
Net current-period other comprehensive income (loss)	28	104
Ending balance	$ (4,560)	$ (7,392)