Consolidated Statements of Comprehensive Income (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Consolidated Statements of Comprehensive Income (Unaudited) [Abstract]
Net income per consolidated statements of income	$ 33,034	$ 29,904	$ 89,021	$ 89,573
Unrealized (losses) gains on available for sale securities:
Unrealized holding (losses) gains arising during the period	(17,461)	2,618	(60,596)	1,834
Less: adjustment for net gains realized in net income	0	0	(233)	(643)
Pension and other postretirement benefit plans:
Change in the net actuarial loss during the period	1,565	976	3,996	2,936
Derivatives:
Change in the accumulated gain on effective cash flow hedge derivatives	(242)	0	1,212	0
Other comprehensive (loss) income, net of tax	(16,138)	3,594	(55,621)	4,127
Comprehensive income	$ 16,896	$ 33,498	$ 33,400	$ 93,700