CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME
Net Income	$ 66,739	$ 63,560	$ 64,151
Net unrealized holding gains on marketable securities:
Unrealized holding (losses)/ gains, net of tax of $10,551, $(1,346) and $(5,996), respectively	(16,544)	2,029	9,312
Other-than-temporary impairment on securities included in net income, net of tax of $(278), $(129) and $(328), respectively	435	202	609
Reclassification adjustment for (gains)/ losses included in net income, net of tax of $1,904, $271 and $(705), respectively	(2,977)	(424)	1,104
Net unrealized holding (losses)/ gains on marketable securities	(19,086)	1,807	11,025
Change in fair value of interest rate swaps, net of tax of $(1,714), $(246) and $1,506, respectively	3,181	459	(2,787)
Defined benefit plans:
Net gain/ (loss), net of tax of $(10,716), $(6,112) and $11,431, respectively	17,002	9,576	(17,863)
Amortization of prior service costs, net of tax of $812, $56 and $56, respectively	(1,509)	(104)	(104)
Net gains/ (loss) on defined benefit plans	15,493	9,472	(17,967)
Other comprehensive (loss)/ income	(412)	11,738	(9,729)
Total comprehensive income	$ 66,327	$ 75,298	$ 54,422