Income Taxes (Details Textual) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Income Tax Examination [Line Items]
Tax benefit from 2006-2009 IRS audit examination closure			$ 5.8
Additions for tax positions related to the current year			0.0	$ 3.0
Additions for tax positions of prior years			0.1	1.0
Reductions for tax positions of prior years			0.0	(0.1)
Unrecognized tax benefits including interest and penalties that would affect the Company's effective tax rate if recognized	$ 5.3	$ 15.2	5.3	15.2
Total accrued interest and penalties related to uncertain tax positions	3.6		3.6		$ 8.9
Increase (decrease) in income tax expense related to interest and penalties on unrecognized tax benefits	0.1	$ 0.4	5.3	0.9
Federal and state tax authorities
Income Tax Examination [Line Items]
Additions for tax positions related to the current year				3.0
State tax authorities
Income Tax Examination [Line Items]
Reductions for tax positions of prior years				$ (0.1)
Settlement with taxing authority and lapse in statute of limitations
Income Tax Examination [Line Items]
Reasonably possible decrease in unrecognized federal and state tax benefits within twelve months	$ 1.3		$ 1.3