Long-Term Debt (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
Credit Facility [Member]
Debt Instrument [Line Items]
Maturity date	2017-12-01
Revolving loans	$ 300
Capacity for the issuance of standby letters of credit	125
Maximum increase in borrowing capacity	150
Variable rate basis of loans under the credit facility	LIBOR
Basis spread on base rate, minimum (in hundredths)	0.75%
Basis spread on base rate, maximum (in hundredths)	1.50%
Letters of credit issued	0.7
Amount available for borrowings	260
Credit Facility [Member] | Minimum [Member]
Debt Instrument [Line Items]
Basis spread on variable rate (in hundredths)	1.75%
Commitment fee for the unused portion of the credit facility (in hundredths)	0.30%
Credit Facility [Member] | Maximum [Member]
Debt Instrument [Line Items]
Basis spread on variable rate (in hundredths)	2.50%
Commitment fee for the unused portion of the credit facility (in hundredths)	0.50%
Senior Secured Term Loan [Member]
Debt Instrument [Line Items]
Face amount	136.9	142.5
Maturity date	2017-12-01
Fair value of debt	136.9	142.5
Quarterly principal payment amount	1.9
Remaining principal amount	$ 114.4
Variable rate basis of loans under the credit facility	LIBOR
Basis spread on variable rate (in hundredths)	1.75%
Basis spread on base rate, minimum (in hundredths)	0.75%