Shareholders' Equity - Disclosure - Shareholders' Equity - Summary of Accumulated Other Comprehensive Loss (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Class of Stock [Line Items]
Balance, beginning of period	$ 6,678	$ 1,264	$ 306
Unrealized holding gains arising during the period	2,134	8,882	1,554
Income tax expense	(810)	(3,371)	(590)
Less: Reclassification adjustment for net gains included in net loss	(10,494)	(157)	(10)
Income tax expense	3,983	60	4
Other Comprehensive Income (Loss)	(5,187)	5,414	958
Balance, end of period	1,491	6,678	1,264
Balance, beginning of period	(9,048)	(7,843)	(7,266)
Change in funded status	1,292	(1,853)	(887)
Income tax benefit	(452)	648	310
Other Comprehensive Income (Loss)	840	(1,205)	(577)
Balance, end of period	(8,208)	(9,048)	(7,843)
Accumulated other comprehensive loss, net	$ (6,717)	$ (2,370)	$ (6,579)