Financial Commitments (Details)	3 Months Ended	9 Months Ended
	Sep. 30, 2015 USD ($)	Sep. 30, 2015 USD ($)	Dec. 31, 2014 USD ($)	Jun. 05, 2014 USD ($)
Term Loan [Member]
Amended Credit Agreement
Issuance date		Jun. 05, 2014
Face amount	$ 250,000,000	$ 250,000,000		$ 200,000,000
Principal payable in year 1 (as a percent)	6.00%	6.00%
Principal payable in year 2 (as a percent)	9.00%	9.00%
Principal payable in year 3 (as a percent)	12.00%	12.00%
Principal payable in year 4 (as a percent)	15.00%	15.00%
Principal payable in year 5 (as a percent)	13.50%	13.50%
Balloon payment at maturity (as a percent)	44.50%	44.50%
Maturity date		Jun. 05, 2019
Loan outstanding	$ 229,400,000	$ 229,400,000	$ 242,500,000
Revolving Credit Facility [Member]
Amended Credit Agreement
Maximum borrowing capacity	300,000,000	300,000,000		300,000,000
Outstanding borrowings	140,000,000	140,000,000	130,000,000
Available borrowing capacity	159,800,000	159,800,000
Letters Of Credit [Member]
Amended Credit Agreement
Sublimit for the issuance of letters of credit	150,000,000	150,000,000
Letters of credit outstanding	200,000	$ 200,000	$ 1,000,000
Revolving Credit Facility And Term Loan [Member]
Amended Credit Agreement
Issuance date		Jun. 05, 2014
Maturity date		Jun. 05, 2019
Covenants duration for maximum allowable consolidated leverage ratio		5 years
Minimum fixed charge ratio		1.25
Revolving Credit Facility And Term Loan [Member] | Minimum [Member[
Amended Credit Agreement
Maximum allowable consolidated leverage ratio		2.75
Revolving Credit Facility And Term Loan [Member] | Maximum [Member]
Amended Credit Agreement
Face amount				$ 300,000,000
Maximum allowable consolidated leverage ratio		3.75
Brightwater Matter [Member]
Amended Credit Agreement
Pre-tax charge	$ 23,900,000