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Revenue Recognition - Narrative (Details) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended |  |
--- | --- | --- | --- | ---
Mar. 31, 2019 | Apr. 01, 2018 | Mar. 31, 2019 | Apr. 01, 2018 | Oct. 01, 2018 | Sep. 30, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |
Decrease to retained earnings upon adoption of new accounting guidance | $ (1,026,836) |  | $ (1,026,836) |  |  | $ (944,965)
Increase to contract assets due to adoption of new accounting guidance | (157,918) |  | (157,918) |  |  | (142,882)
Contracts liabilities | (154,609) |  | (154,609) |  |  | (143,270)
Increase to deferred tax assets due to adoption of new accounting guidance | 30,581 |  | 30,581 |  |  | 8,607
Contract liability revenue recognized during the period |  |  | 74,200 |  |  |
Liabilities for anticipated losses | 11,700 |  | 11,700 |  |  | $ 13,600
Estimated cost to complete the related contracts | 11,700 |  | 11,700 |  |  |
Impact of the Adoption of ASC 606 | Accounting Standards Update 2014-09 |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |
Decrease to retained earnings upon adoption of new accounting guidance |  |  |  |  | $ 2,800 |
Increase to contract assets due to adoption of new accounting guidance |  |  |  |  | 5,000 |
Contracts liabilities |  |  |  |  | 1,100 |
Increase to deferred tax assets due to adoption of new accounting guidance |  |  |  |  | $ 1,100 |
CIG |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |
Net unfavorable operating income adjustments | $ 2,800 | $ 700 | $ 3,200 | $ 1,400 |  |

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