Income Taxes - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Income Tax Contingency [Line Items]
Effective income tax rates	15.30%	1.30%	6.40%	(3.00%)
Depreciable life for amortization of tax expense			20 years
Prepaid tax asset, net of amortization	$ 323.7		$ 323.7		$ 190.1
Unrecognized Tax Benefits	1.5		1.5		1.5
Unrecognized Tax Benefits Income Tax Penalties And Interest Accrued	$ 0.3		$ 0.3		0.3
State
Income Tax Contingency [Line Items]
Net operating loss carryforwards					546.6
Net operating loss carryforwards, Year of expiration			2020
Federal
Income Tax Contingency [Line Items]
Net operating loss carryforwards					$ 595.0
Net operating loss carryforwards, Year of expiration			2028