Financial Commitments (Details) (USD $)	9 Months Ended						9 Months Ended
	Sep. 30, 2014 Term Loan [Member]	Jun. 05, 2014 Term Loan [Member]	Sep. 30, 2014 Revolving credit agreement [Member]	Dec. 31, 2013 Revolving credit agreement [Member]	Sep. 30, 2014 Letters of credit [Member]	Dec. 31, 2013 Letters of credit [Member]	Sep. 30, 2014 Revolving Credit Facility and Term Loan [Member]	Sep. 30, 2014 Revolving Credit Facility and Term Loan [Member] Minimum [Member[	Sep. 30, 2014 Revolving Credit Facility and Term Loan [Member] Maximum [Member]
Amended Credit Agreement
Maximum borrowing capacity			$ 300,000,000
Debt issuance date	Jun. 05, 2014
Principal payable in year 1 (as a percent)	6.00%
Principal payable in year 2 (as a percent)	9.00%
Principal payable in year 3 (as a percent)	12.00%
Principal payable in year 4 (as a percent)	15.00%
Principal payable in year 5 (as a percent)	13.50%
Balloon payment at maturity (as a percent)	44.50%
Debt Instrument, Maturity Date	Jun. 05, 2019						Jun. 05, 2019
First payment due date	Sep. 30, 2014
Sublimit for the issuance of letters of credit					150,000,000
Maximum allowable consolidated leverage ratio								2.75	3.75
Covenants duration for maximum allowable consolidated leverage ratio							5 years
Minimum fixed charge ratio							1.25
Face amount	250,000,000
Loan outstanding	246,300,000	200,000,000
Outstanding borrowings			205,500,000	135,000,000
Letters of credit outstanding					1,300,000	200,000
Available borrowing capacity			$ 93,200,000