Consolidated Statements of Comprehensive Income (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Consolidated Statements of Comprehensive Income (Unaudited) [Abstract]
Net income per consolidated statements of income	$ 31,121	$ 29,349	$ 55,987	$ 59,669
Unrealized (losses) gains on available for sale securities:
Unrealized holding (losses) gains arising during the period	(44,515)	1,132	(43,135)	(784)
Less: adjustment for net (gains) losses realized in net income	(107)	5	(233)	(643)
Pension and other postretirement benefit plans:
Change in the net actuarial loss during the period	1,371	980	2,431	1,960
Derivatives:
Change in the accumulated gain on effective cash flow hedge derivatives	1,454	0	1,454	0
Other comprehensive (loss) income, net of tax	(41,797)	2,117	(39,483)	533
Comprehensive (loss) income	$ (10,676)	$ 31,466	$ 16,504	$ 60,202