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Debt And Liquidity (Old Revolving Facility and Term Loan Facility) (Details) - USD ($) | Feb. 27, 2015 | Dec. 31, 2018 | Dec. 31, 2017 | Apr. 27, 2016 | Aug. 11, 2015 | Jul. 28, 2015 | Apr. 23, 2014 | Nov. 20, 2012
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Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Minimum Liquidity |  |  |  | $ 25,000,000 |  |  |  |
12 Month Trailing EBITDA |  |  | $ 75,000,000 |  |  |  |  |
12 Month Trailing EBITDA Minimum (High End) |  |  |  | 35,000,000 |  |  |  |
Term Loan Balance |  |  |  |  | $ 40,000,000 |  |  |
Debt Instrument, Interest Rate, Stated Percentage |  | 6.375% |  |  |  |  |  |
Revolving Credit Facility [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Long-term Line of Credit |  | $ 0 | 58,192,000 |  |  |  |  |
Letters of Credit Outstanding, Amount |  |  | 48,200,000 |  |  |  |  |
Revolving Credit Facility [Member] | Amended and Restated Credit Agreement February 2015 [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Line of Credit Facility, Maximum Borrowing Capacity |  |  |  |  |  |  | $ 400,000,000 |
Revolving Credit Facility [Member] | Amended and Restated Credit Agreement July 2015 [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Line of Credit Facility, Maximum Borrowing Capacity |  |  |  | $ 225,000,000 |  | $ 375,000,000 |  |
Long-term Line of Credit |  |  | 39,500,000 |  |  |  |  |
Letters of Credit Outstanding, Amount |  |  | 8,700,000 |  |  |  |  |
Term Loan Facility [Member] | Amended and Restated Credit Agreement February 2015 [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Line of Credit Facility, Maximum Borrowing Capacity | $ 40,000,000 |  |  |  |  |  |  |
Minimum [Member] | Amended and Restated Credit Agreement February 2015 [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage | 0.35% |  |  |  |  |  |  |
Minimum [Member] | London Interbank Offered Rate (LIBOR) [Member] | Amended and Restated Credit Agreement February 2015 [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Debt Instrument, Basis Spread on Variable Rate | 2.25% |  |  |  |  |  |  |
Maximum | Amended and Restated Credit Agreement February 2015 [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage | 0.70% |  |  |  |  |  |  |
Maximum | London Interbank Offered Rate (LIBOR) [Member] | Amended and Restated Credit Agreement February 2015 [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Debt Instrument, Basis Spread on Variable Rate | 4.75% |  |  |  |  |  |  |
Senior Notes [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Debt Instrument, Face Amount |  |  |  |  |  |  |  | $ 300,000,000
Debt Instrument, Interest Rate, Stated Percentage |  |  |  |  |  |  |  | 6.375%
Repurchase Percentage Price Of Aggregate Principal Due To Change In Control |  |  |  |  |  |  |  | 101.00%
Senior Notes [Member] | Minimum [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Unpaid Indebtness After Maturity Or Acceleration |  |  | $ 50,000,000.0 |  |  |  |  |

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- Definition 12 Month Trailing EBITDA + References No definition available. + Details
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- Definition 12 Month Trailing EBITDA Minimum (High End) + References No definition available. + Details
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- Definition Minimum liquidity required by credit facility + References No definition available. + Details
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- Definition Repurchase Percentage Price Of Aggregate Principal Due To Change In Control + References No definition available. + Details
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- Definition Term loan portion of revolving credit facility balance + References No definition available. + Details
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- Definition Percentage points added to the reference rate to compute the variable rate on the debt instrument. + References No definition available. + Details
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- Definition Face (par) amount of debt instrument at time of issuance. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 55 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400 + Details
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- Definition Contractual interest rate for funds borrowed, under the debt agreement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(1)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition The total amount of the contingent obligation under letters of credit outstanding as of the reporting date. + References No definition available. + Details
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- Definition The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(22)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(16)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(16)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 + Details
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- Definition Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b),22(b)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility. + References No definition available. + Details
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