CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME [Abstract]
Net income	$ 5,662		$ 6,583
Unrealized (losses) gains on securities available-for-sale:
Unrealized holding losses on securities available-for-sale arising during period, net of related tax effects of $1,507 and $656	(2,799)		(1,219)
Less: reclassification adjustment for gains included in net income, net of related tax effects of $48 and $42	(90)		(79)
Net change in unrealized gains on securities available-for-sale	(2,889)		(1,298)
Unrealized gain on cash flow hedging derivatives, net of related tax effects of ($458) and ($821)	850		1,525
Postretirement plans:
Net actuarial gain arising during period, net of related tax effects of ($21) and ($13)	39		24
Plus: amortization of prior service cost included in net periodic cost, net of related tax effects of ($4) and ($2)	8	[1]	3	[1]
Other comprehensive (loss) income	(1,992)		254
Comprehensive income	$ 3,670		$ 6,837

[1] Reclassified into the consolidated statements of income in salaries and employee benefits.