Benefit Plans (Details Textual) $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($) noncontributory_defined_benefit_pension_plans	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Compensation and Retirement Disclosure [Abstract]
Employer discretionary contribution amount	$ 3.8	$ 3.2	$ 3.4
Number of non-contributory defined benefit pension plans | noncontributory_defined_benefit_pension_plans	2
Period of average compensation for pension benefit computation	5 years
Age limit for a lump sum payment	55 years
Deferred compensation arrangement with Individual, recorded liability	$ 7.4
Long-term portion of the pension liability	25.1	24.9
AOCI net prior service cost	3.0
Future amortization of prior service cost	$ 0.2
Retirement age	65 years
Expense related to contributions	$ 0.1	0.3	$ 0.2
Total deferred compensation liability	13.8	11.0
Deferred compensation liability, current	$ 1.2	$ 0.9