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Borrowing Arrangements (Narrative) (Details) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended | 9 Months Ended |  |
--- | --- | --- | --- | --- | ---
Jun. 30, 2018 | Jun. 30, 2017 | Mar. 31, 2018 | Jun. 30, 2018 | Jun. 30, 2017 | Sep. 30, 2018 | Sep. 30, 2017
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Minimum (Deprecated 2016-01-31) | 5.50% |  |  | 5.50% |  |  |
Debt Instrument, Fair Value Disclosure | $ 452,300 |  |  | $ 452,300 |  |  |
Debt Instrument, Redemption Period, End Date |  |  |  | Jun. 15, 2021 |  |  |
Debt Instrument, Redemption Period, Start Date |  |  |  | Jun. 15, 2021 |  |  |
Debt Instrument, Redemption Price, Percentage of Principal Amount Redeemed |  |  |  | 40.00% |  |  |
Debt Instrument, Redemption Price, Percentage |  |  |  | 101.00% |  |  |
Future maturities of outstanding borrowings |  |  |  |  |  |  |
Loss on early extinguishment of debt | 6,200 | $ 0 |  | $ 6,200 | $ 0 |  |
Debt Instrument, Issuance Date |  |  |  | Jun. 12, 2018 |  |  |
5.5% Senior Notes | 450,000 |  |  | $ 450,000 |  |  | $ 0
Debt Instrument, Repurchase Date |  |  |  | Jun. 12, 2018 |  |  |
Domestic Line of Credit [Member] |  |  |  |  |  |  |
Revolving credit facility amount | $ (225,000) |  |  | $ (225,000) |  |  |
Potential increase size of the credit facility by an additional amount |  |  |  | $ 150,000 |  |  |
Line of Credit Facility, Interest Rate at Period End | 12500.00% |  |  | 12500.00% |  |  |
Agreement termination date |  |  |  | Jul. 13, 2021 |  |  |
Aggregate commitments availability |  |  |  | $ 17,500 |  |  |
Aggregate commitments availability, percentage |  |  |  | 10.00% |  |  |
Outstanding letter of credit accrued fees and expenses | $ 18,100 |  |  | $ 18,100 |  |  |
Excess availability reduced by outstanding borrowings, outstanding letters of credit and accrued fees and expenses | 112,000 |  |  | 112,000 |  |  |
Swing Line Loans [Member] |  |  |  |  |  |  |
Revolving credit facility amount | (25,000) |  |  | (25,000) |  |  |
Letters Of Credit Outstanding [Member] |  |  |  |  |  |  |
Revolving credit facility amount | (60,000) |  |  | (60,000) |  |  |
Secured Debt [Member] |  |  |  |  |  |  |
Long-term Debt, Gross | $ 500,000 |  |  | $ 500,000 |  |  |
Debt Instrument, Basis Spread on Variable Rate |  |  | 25000.00% |  |  |  |
Debt Instrument, Periodic Payment, Principal |  |  | $ 1,225 |  |  |  |
Agreement termination date |  |  | Nov. 25, 2021 |  |  |  |
Minimum [Member] | Domestic Line of Credit [Member] |  |  |  |  |  |  |
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage |  |  |  | 2500.00% |  |  |
London Interbank Offered Rate (LIBOR) [Member] | Minimum [Member] | Long-term Debt [Member] |  |  |  |  |  |  |
Debt Instrument, Basis Spread on Variable Rate |  |  |  | 2500.00% |  |  |
London Interbank Offered Rate (LIBOR) [Member] | Minimum [Member] | Domestic Line of Credit [Member] |  |  |  |  |  |  |
Debt Instrument, Basis Spread on Variable Rate |  |  |  | 12500.00% |  |  |
London Interbank Offered Rate (LIBOR) [Member] | Minimum [Member] | Secured Debt [Member] |  |  |  |  |  |  |
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Minimum (Deprecated 2016-01-31) | 0.75% |  |  | 0.75% |  |  |
London Interbank Offered Rate (LIBOR) [Member] | Maximum [Member] | Domestic Line of Credit [Member] |  |  |  |  |  |  |
Debt Instrument, Basis Spread on Variable Rate |  |  |  | 15000.00% |  |  |
Base Rate [Member] | Maximum [Member] | Domestic Line of Credit [Member] |  |  |  |  |  |  |
Debt Instrument, Basis Spread on Variable Rate |  |  |  | 5000.00% |  |  |
Subsequent Event [Member] | Domestic Line of Credit [Member] |  |  |  |  |  |  |
Revolving credit facility amount |  |  |  |  |  | $ (175,000) |
Line of credit facility, Reduction of Borrowing Capacity |  |  |  |  |  | $ 50,000 |

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- Definition Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -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://www.xbrl.org/2003/role/presentationRef -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 Reference 3: http://www.xbrl.org/2003/role/presentationRef -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 + Details
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