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Debt - 2017 Senior Notes (Details) - USD ($) | Feb. 21, 2017 | Oct. 24, 2014 | Sep. 30, 2020 | Sep. 29, 2016 | Oct. 17, 2014
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Term loan B |  |  |  |  |
Debt |  |  |  |  |
Amount of debt redeemed | $ 127,600,000 |  |  |  |
Term loan A |  |  |  |  |
Debt |  |  |  |  |
Face amount |  |  |  | $ 185,000,000.0 |
Amount of debt redeemed | 600,000,000 |  |  |  |
Revolving credit facility |  |  |  |  |
Debt |  |  |  |  |
Amount of debt redeemed | 250,000,000 |  |  |  |
2017 Senior Notes |  |  |  |  |
Debt |  |  |  |  |
Face amount | $ 1,000,000,000 |  |  |  |
Fair value of debt instrument |  |  | $ 1,069,600,000 |  |
Interest rate (as a percent) | 5.125% |  |  |  |
2017 Senior Notes | At any time and from time to time prior to December 15, 2026 |  |  |  |  |
Debt |  |  |  |  |
Redemption price (in percent) | 100.00% |  |  |  |
2017 Senior Notes | At any time on or after December 15, 2026 |  |  |  |  |
Debt |  |  |  |  |
Redemption price (in percent) | 100.00% |  |  |  |
URS Senior Notes |  |  |  |  |
Debt |  |  |  |  |
Face amount |  |  |  |  | $ 1,000,000,000.0
Amount of debt redeemed |  | $ 572,300,000 |  |  |
Redemption price (as percent of principal) |  | 101.00% |  |  |

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