Pension Benefit and Other Postretirement Benefit Plans (Fair Value of Net Assets by Asset Category) (Details) (Pension Benefits [Member], USD $) In Thousands, unless otherwise specified	Jun. 30, 2013		Apr. 30, 2013		Dec. 31, 2012
Defined Benefit Plan Disclosure [Line Items]
Pension assets	$ 157,379	[1]	$ 156,741	[2]	$ 143,540	[1],[2]
Pooled separate accounts [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension assets			33,530	[2]	29,869	[2]
Mutual funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension assets			106,619	[2]	98,269	[2]
Guaranteed deposit account [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension assets			$ 16,592	[2]	$ 15,402	[2]

[1] This calculation was performed as of June 30, 2013 due to the pension freeze and we are not otherwise required to perform the calculation at interim periods

[2] This calculation was performed as of April 30, 2013 due to the pension freeze and we are not otherwise required to perform the calculation at interim periods