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Debt And Liquidity (Narrative) (Details) - USD ($)	Feb. 27, 2015	Jun. 30, 2017	Dec. 31, 2016	Apr. 27, 2016	Jul. 28, 2015	Apr. 23, 2014	Nov. 20, 2012
Debt Instrument [Line Items]
Fair value of debt		$ 363,900,000
Long-term Debt		375,963,000	$ 365,432,000
Minimum Liquidity				$ 25,000,000
Outstanding letters of credit		14,100,000
Term Loan Balance		29,500,000
Revolving Credit Facility Balance		$ 68,500,000
Stated interest rate		6.375%
Loan balance, net of unamortized discount		$ 8,007,000	8,852,000
12 Month Trailing EBITDA			75,000,000
12 Month Trailing EBITDA Minimum (Low End)				40,000,000
12 Month Trailing EBITDA Minimum (High End)				35,000,000
Senior Notes
Debt Instrument [Line Items]
Long-term Debt		277,341,000	$ 274,132,000
Principal amount issued							$ 300,000,000
Stated interest rate							6.375%
Redemption price, percentage of principal, prior to November 15, 2016							100.00%
Repurchase price, percentage of principal, due to change in control							101.00%
Minimum | Senior Notes
Debt Instrument [Line Items]
Unpaid indebtedness or accelerated proceeds exceeds		50,000,000
Unpaid judgment or decree in excess of		$ 50,000,000
Amended and Restated Credit Agreement | Minimum
Debt Instrument [Line Items]
Undrawn commitment fee	0.35%
Amended and Restated Credit Agreement | Maximum
Debt Instrument [Line Items]
Undrawn commitment fee	0.70%
Amended and Restated Credit Agreement | LIBOR | Minimum
Debt Instrument [Line Items]
Margin spread on variable interest rate	2.25%
Amended and Restated Credit Agreement | LIBOR | Maximum
Debt Instrument [Line Items]
Margin spread on variable interest rate	4.75%
Amended and Restated Credit Agreement | Revolving Credit Facility
Debt Instrument [Line Items]
Borrowing capacity						$ 400,000,000
Amended and Restated Credit Agreement | Term Loan Facility
Debt Instrument [Line Items]
Borrowing capacity	$ 40,000,000
Amended and Restated Credit Agreement July 2015 [Member] | Revolving Credit Facility
Debt Instrument [Line Items]
Borrowing capacity				$ 225,000,000	$ 375,000,000
Amended and Restated Credit Agreement July 2015 [Member] | Term Loan Facility
Debt Instrument [Line Items]
Borrowing capacity					$ 40,000,000

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