Income Taxes - Schedule of Income Tax Amounts were Recorded in Shareholder's Equity as Elements of Other Comprehensive Income (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Securities and defined benefit pension plan unrecognized items	$ (3,538)	$ (3,707)	$ (3,192)