Consolidated Statements of Comprehensive Income (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Consolidated Statements of Comprehensive Income (Unaudited) [Abstract]
Net income per consolidated statements of income	$ 33,589	$ 33,034	$ 95,489	$ 89,021
Unrealized gains (losses) on available for sale securities and transferred securities:
Unrealized holding (losses) gains arising during the period	(5,182)	(17,461)	5,814	(60,596)
Less: adjustment for net losses (gains) realized in net income	55	0	(185)	(233)
Change in net unrealized holding losses on securities transferred to held to maturity	1,011	0	2,744	0
Pension and other postretirement benefit plans:
Net change in prior service costs	39	38	116	116
Recognized net loss due to settlement	1,055	518	1,518	842
Recognized net actuarial (gain) loss	(949)	1,009	166	3,038
Derivatives:
Change in the accumulated gain on effective cash flow hedge derivatives	163	(242)	(807)	1,212
Other comprehensive (loss) income, net of tax	(3,808)	(16,138)	9,366	(55,621)
Comprehensive income	$ 29,781	$ 16,896	$ 104,855	$ 33,400