Consolidated Statements of Comprehensive Income (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Consolidated Statements of Comprehensive Income (Unaudited) [Abstract]
Net income per consolidated statements of income	$ 29,003	$ 24,866
Unrealized (losses) gains on available for sale securities and transferred securities:
Unrealized holding gains arising during the period	4,229	1,380
Less: adjustment for net gains realized in net income	(240)	(126)
Change in net unrealized holding loss on securities transferred to held to maturity	823	0
Pension and other postretirement benefit plans:
Net change in prior service costs	39	39
Recognized net loss due to settlement	232	0
Recognized net actuarial loss	559	1,021
Derivatives:
Change in the accumulated gain on effective cash flow hedge derivatives	(408)	0
Other comprehensive income, net of tax:	5,234	2,314
Comprehensive income	$ 34,237	$ 27,180