Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Consolidated Statements of Comprehensive Income (Unaudited) [Abstract]
Net income per consolidated statements of income	$ 30,602	$ 32,897	$ 59,750	$ 61,900
Unrealized (losses) gains on available for sale securities and transferred securities:
Unrealized holding (losses) gains arising during the period	(13,951)	6,767	(2,565)	10,996
Less: adjustment for net gains realized in net income	0	0	0	(240)
Change in net unrealized holding losses on securities transferred to held to maturity	1,021	910	1,895	1,733
Pension and other postretirement benefit plans:
Net change in prior service costs	38	38	77	77
Recognized net loss due to lump sum settlement	296	231	553	463
Change in net actuarial loss	751	556	1,505	1,115
Derivatives:
Change in the accumulated loss on effective cash flow hedge derivatives	174	(562)	(434)	(970)
Less: adjustment for loss realized in net income	130	0	260	0
Other comprehensive (loss) income, net of tax	(11,541)	7,940	1,291	13,174
Comprehensive income	$ 19,061	$ 40,837	$ 61,041	$ 75,074