Income Taxes - Schedule of Income Tax Amounts were Recorded in Shareholder's Equity as Elements of Other Comprehensive Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Securities and defined benefit pension plan unrecognized items	$ (3,480)	$ (1,202)	$ (3,538)