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Income Taxes (Details 2) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Sep. 30, 2015 | Sep. 30, 2014
Income Taxes, additional disclosures |  |
Unused federal and state research and development credits which can be carried forward indefinitely | $ 22.4 |
California Enterprise Zone Tax Credits which can be carried forward indefinitely | 6.8 |
Net deferred tax asset likely to be realized and for which no additional valuation allowance has been provided | 657.3 |
Valuation allowance increase | 212.0 |
Additional valuation allowance provided for, net deferred tax asset which is likely to be realized | 95.2 |
Undistributed earnings from non-U.S. subsidiaries | 1,341.2 |
Deferred tax liability of foreign subsidiaries | 88.2 |
Liability for unrecognized tax benefits, including potential interest and penalties, net of related tax benefit | 107.6 | $ 52.6
Unrecognized tax benefits that would be included in the effective tax rate if recognized | 77.0 |
Reconciliation of the beginning and ending amount of gross unrecognized tax benefits |  |
Balance at the beginning of the year | 47.5 | 53.7
Gross increase due to acquisitions | 49.4 |
Gross increase in prior years' tax positions | 6.4 | 3.3
Gross decrease in prior years' tax positions | (0.2) | (7.6)
Decrease due to settlement with tax authorities | (2.0) | (2.0)
Gross increase in current periods tax positions | 6.0 | 2.2
Decrease due to lapse of statute of limitations | (4.6) | (2.1)
Gross change due to foreign exchange fluctuations | (7.3) |
Balance at the end of the year | 95.2 | 47.5
Deferred tax assets: |  |
Compensation and benefit accruals not currently deductible | 166.7 | 65.5
Net operating loss carry forwards | 195.9 | 69.3
Self insurance reserves | 46.8 | 48.8
Research and experimentation and other tax credits | 43.0 | 34.2
Pension liability | 165.6 | 59.4
Accrued liabilities | 267.3 | 63.7
Other | 11.4 | 26.2
Total deferred tax assets | 896.7 | 367.1
Decrease in deferred tax asset | 34.8 |
Deferred tax liabilities: |  |
Unearned revenue | (101.9) | (122.9)
Depreciation and amortization | (76.5) | (59.2)
Acquired intangible assets | (219.2) | (14.8)
Investment in subsidiaries | (239.2) |
Total deferred tax liabilities | (636.8) | (196.9)
Valuation allowance | (239.4) | (27.1)
Net deferred tax asset | 20.5 |
Net deferred tax assets |  | 143.1
Accrued penalties, excluding any related income tax benefits | 3.5 | 2.9
Accrued interest, excluding any related income tax benefits | 13.9 | 6.2
Tax-deductible goodwill | 261.2 | $ 251.6
URS Corporation |  |
Income Taxes, additional disclosures |  |
Valuation allowance increase | 182.0 |
Deferred tax liability related to stock basis adjustment | $ 145.6 |
Maximum |  |
Deferred tax liabilities: |  |
Period of amortization of goodwill | 15 years |
State and Local Jurisdiction |  |
Deferred tax liabilities: |  |
Net operating loss carry forwards | $ 526.0 |
Foreign Tax Authority |  |
Deferred tax liabilities: |  |
Net operating loss carry forwards | $ 828.7 |

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- Definition Amount of decrease in unrecognized tax benefits resulting from tax positions taken in prior period tax returns. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15A -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6907707&loc=SL6600010-109319 + Details
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- Definition Amount of decrease in unrecognized tax benefits resulting from settlements with taxing authorities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15A -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=6907707&loc=SL6600010-109319 + Details
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- Definition Amount of statutory penalties accrued for a tax position claimed or expected to be claimed by the entity, in its tax return. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32718-109319 + Details
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- Definition Amount of increase in unrecognized tax benefits resulting from tax positions taken in prior period tax returns. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15A -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6907707&loc=SL6600010-109319 + Details
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- Definition Amount of interest expense accrued for an underpayment of income taxes. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32718-109319 + Details
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- Definition Amount of decrease in unrecognized tax benefits resulting from lapses of applicable statutes of limitations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15A -Subparagraph (a)(4) -URI http://asc.fasb.org/extlink&oid=6907707&loc=SL6600010-109319 + Details
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- Definition The total amount of unrecognized tax benefits that, if recognized, would affect the effective tax rate. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6907707&loc=SL6600010-109319 + Details
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