Consolidated Statements of Income and Comprehensive Income (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Statement [Abstract]
Reclassifications for unrealized net gains on available-for-sale securities	$ 4,520	$ 4,513	$ 5,085
Reclassification adjustment for employee benefit costs	5,486	7,468	3,072
Income tax effect	$ 338	$ 1,034	$ (704)