Pension and Other Postretirement Benefit Plans (Tables)

9 Months Ended

Sep. 30, 2012

Compensation and Retirement Disclosure [Abstract]

Components of net periodic benefit cost (income) for the Corporation's qualified and nonqualified pension plans and nonqualified postretirement benefits plan

	Three Months Ended						Nine Months Ended
	September 30,						September 30,
	2012			2011			2012			2011
	(In thousands)
Defined Benefit Pension Plans
Service cost	$	304		$	290		$	910		$	872
Interest cost	1,214			1,207			3,644			3,622
Expected return on plan assets	(1,731		)	(1,582		)	(5,194		)	(4,746		)
Amortization of prior service credit	—			—			(1		)	(1		)
Amortization of unrecognized net loss	614			270			1,843			809
Net periodic benefit cost	$	401		$	185		$	1,202		$	556
Postretirement Benefit Plan
Interest cost	$	37		$	42		$	110		$	125
Amortization of prior service credit	(75		)	(81		)	(225		)	(243		)
Amortization of unrecognized net gain	(7		)	(8		)	(21		)	(24		)
Net periodic benefit income	$	(45	)	$	(47	)	$	(136	)	$	(142	)