Other Comprehensive Income - Amounts Reclassified Out of Each Component of Accumulated Other Comprehensive Loss (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income tax expense	$ (677)	$ (309)	$ (1,577)	$ (891)
Net income available to common shareholders	1,834	1,367	3,890	2,990
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income available to common shareholders	12	(92)	(14)	(185)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Unrealized Gains and Losses on Available-for-Sale Securities [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Unrealized gains and losses on available-for-sale securities	107	41	112	58
Income tax expense	(36)	(14)	(38)	(20)
Net income available to common shareholders	71	27	74	38
Reclassification out of Accumulated Other Comprehensive Income [Member] | Defined Benefit Pension Items [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Actuarial gains/(losses)	(89)	(180)	(132)	(338)
Income tax expense	30	61	44	115
Net income available to common shareholders	$ (59)	$ (119)	$ (88)	$ (223)