Pension and Postretirement Benefits (Details 3) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Amounts recognized in accumulated other comprehensive income
Net actuarial loss	$ 20,306	$ 19,178
Prior service credit	(2,900)	(4,013)
Subtotal	17,406	15,165
Less tax effect	(6,601)	(5,792)
Total	10,805	9,373
Postretirement Benefit Plans [Member]
Amounts recognized in accumulated other comprehensive income
Net actuarial loss	6,706	7,029
Prior service credit	(2,900)	(4,013)
Subtotal	3,806	3,016
Less tax effect	(1,443)	(1,153)
Total	2,363	1,863
Funded Plans [Member]
Amounts recognized in accumulated other comprehensive income
Net actuarial loss	9,052	8,238
Prior service credit
Subtotal	9,052	8,238
Less tax effect	(3,433)	(3,146)
Total	5,619	5,092
Unfunded Pension Plans [Member]
Amounts recognized in accumulated other comprehensive income
Net actuarial loss	4,548	3,911
Prior service credit
Subtotal	4,548	3,911
Less tax effect	(1,725)	(1,493)
Total	$ 2,823	$ 2,418