Consolidated Statements of Comprehensive Income (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Consolidated Statements of Comprehensive Income (Unaudited) [Abstract]
Net income per consolidated statements of income	$ 32,897	$ 31,121	$ 61,900	$ 55,987
Unrealized gains (losses) on available for sale securities and transferred securities:
Unrealized holding gains (losses) arising during the period	6,767	(44,515)	10,996	(43,135)
Less: adjustment for net gains realized in net income	0	(107)	(240)	(233)
Change in net unrealized holding loss on securities transferred to held to maturity	910	0	1,733	0
Pension and other postretirement benefit plans:
Net change in prior service costs	38	39	77	78
Recognized net loss due to settlement	231	324	463	324
Recognized net actuarial loss	556	1,008	1,115	2,029
Derivatives:
Change in the accumulated gain on effective cash flow hedge derivatives	(562)	1,454	(970)	1,454
Other comprehensive income (loss), net of tax	7,940	(41,797)	13,174	(39,483)
Comprehensive income (loss)	$ 40,837	$ (10,676)	$ 75,074	$ 16,504