Benefit Plans (Details Textual) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Defined Benefit Plan Disclosure [Line Items]
AllocatedShareBasedCompensationExpense	$ 1,500,000	$ 1,200,000	$ 1,400,000
Noncontributory defined benefit pension plans
Defined Benefit Plan Disclosure [Line Items]
PensionAndOtherPostretirementBenefitExpense	7,300,000	5,700,000	6,100,000
OtherPostretirementBenefitPlansDefinedBenefitMember
Defined Benefit Plan Disclosure [Line Items]
PensionAndOtherPostretirementBenefitExpense	0.0	0.0	0.0
DefinedContributionPensionMember
Defined Benefit Plan Disclosure [Line Items]
PensionAndOtherPostretirementBenefitExpense	$ 2,500,000	$ 2,400,000	$ 2,200,000