Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Statement of Comprehensive Income [Abstract]
Net change in Unrealized gains,tax expense	$ 6,479	$ 2,794
Reclassification adjustment for gains, tax expense	116	171
Amortization of unrealized gain on securities reclassified to held-to-maturity, tax benefit	65	0
Change in unfunded pension liability related to unrealized gain (loss), prior service cost and transition obligation, tax (benefit) expense	$ 306	$ (9)