Derivative Financial Instruments (Details) MMBTU in Millions, $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2015 USD ($) MMBTU counterparty	Dec. 31, 2014 USD ($) MMBTU counterparty
Designated as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives	$ 0.1	$ 0.1
Liability Derivatives	$ 2.7	$ 3.5
Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Underlying risk	change in natural gas prices
Period through which natural gas is hedged	Dec. 31, 2016
Percent of forecasted usage to be hedged (up to 90%)	90.00%
Maximum period which the Company hedges in advance of forecasted purchase	36 months
Notional amount (in MMBtus) | MMBTU	1.9	3.4
Net losses to be reclassified from accumulated other comprehensive loss to earnings during the next 12 months	$ 2.1
Number of counterparties | counterparty	4	4
Number of counterparties for amounts recorded as liabilities | counterparty	3
Number of counterparties for amounts recorded as assets | counterparty		2
Netting of contracts in a receivable position against contracts in payable position		$ 0.1
Commodity Contracts [Member] | Designated as Hedging Instruments [Member] | Other Current Asset [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives	$ 0.1	0.1
Commodity Contracts [Member] | Designated as Hedging Instruments [Member] | Other Assets [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives	0.0	0.0
Commodity Contracts [Member] | Designated as Hedging Instruments [Member] | Accrued Expenses [Member]
Derivatives, Fair Value [Line Items]
Liability Derivatives	2.2	2.5
Commodity Contracts [Member] | Designated as Hedging Instruments [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Liability Derivatives	$ 0.5	$ 1.0