Derivative and Hedging Activities	9 Months Ended
Sep. 27, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative and Hedging Activities	Derivative and Hedging Activities The Company has historically entered into interest rate swap agreements to reduce its exposure to the variable rate portion of its long-term debt. The Company also considers counterparty credit risk and its own credit risk in its determination of all estimated fair values. The Company has historically entered into derivative instruments covered by master netting arrangements whereby, in the event of a default as defined by the 2018 Credit Agreement (as defined below) or termination event, the non-defaulting party has the right to offset any amounts payable against any obligation of the defaulting party under the same counterparty agreement. See Note 15, Debt, for more information. Interest Rate Swaps On March 15, 2017, the Company entered into an interest rate swap agreement, with an effective date of March 31, 2017. The swaps have a notional value of $250.0 and fix the variable portion of the Company’s floating rate debt at 1.815%. The fair value of the interest rate swaps, using Level 2 inputs, was an asset of $3.5 and $0.9 as of September 27, 2018 and December 31, 2017, respectively. The Company recorded a net gain related to swap activity of $0.3 and $2.6, for the three and nine months ended September 27, 2018, respectively. Foreign Currency Forward Contract As described further in Note 23, Asco Acquisition, the Company and its wholly-owned subsidiary Spirit AeroSystems Belgium Holdings BVBA (“Spirit Belgium”) entered into a definitive agreement (the “Purchase Agreement”) with certain private sellers pursuant to which Spirit Belgium will purchase all of the issued and outstanding equity of S.R.I.F. N.V., the parent company of Asco Industries N.V. (“Asco”) for $650.0 in cash, subject to certain customary closing adjustments, including foreign currency adjustments. As such, movements in the Euro exchange rates could cause the purchase price to fluctuate, affecting our cash flows. To reduce the Company's exposure to currency exchange rate fluctuations, the Company entered into foreign currency forward contracts. The objective of these contracts is to minimize the impact of currency exchange rate movements on the Company's cash flows, however the Company has not designated these forward contracts as a hedge and has not applied hedge accounting to them. During the second quarter of 2018, to reduce the Euro exchange rate exposure of the purchase of Asco, the Company entered into a foreign currency forward contract in the amount of $580.0; this foreign currency forward contract was settled in the third quarter of 2018. Additionally, during the third quarter of 2018, to reduce the Euro exchange rate exposure of the purchase of Asco, the Company entered into a foreign currency forward contract in the amount of $568.3. The fair value of the foreign currency forward contract, using Level 2 inputs, was a liability of $6.0 as of September 27, 2018. The Company recorded a net gain related to foreign currency forward contract activity of $0.8 for the three months ended September 27, 2018 and a net loss of $20.7 for the nine months ended September 27, 2018.

Derivative and Hedging Activities

The Company has historically entered into interest rate swap agreements to reduce its exposure to the variable rate portion of its long-term debt. The Company also considers counterparty credit risk and its own credit risk in its determination of all estimated fair values.

The Company has historically entered into derivative instruments covered by master netting arrangements whereby, in the event of a default as defined by the 2018 Credit Agreement (as defined below) or termination event, the non-defaulting party has the right to offset any amounts payable against any obligation of the defaulting party under the same counterparty agreement. See Note 15, Debt, for more information.

Interest Rate Swaps

On March 15, 2017, the Company entered into an interest rate swap agreement, with an effective date of March 31, 2017. The swaps have a notional value of $250.0 and fix the variable portion of the Company’s floating rate debt at 1.815%. The fair value of the interest rate swaps, using Level 2 inputs, was an asset of $3.5 and $0.9 as of September 27, 2018 and December 31, 2017, respectively. The Company recorded a net gain related to swap activity of $0.3 and $2.6, for the three and nine months ended September 27, 2018, respectively.

Foreign Currency Forward Contract

As described further in Note 23, Asco Acquisition, the Company and its wholly-owned subsidiary Spirit AeroSystems Belgium Holdings BVBA (“Spirit Belgium”) entered into a definitive agreement (the “Purchase Agreement”) with certain private sellers pursuant to which Spirit Belgium will purchase all of the issued and outstanding equity of S.R.I.F. N.V., the parent company of Asco Industries N.V. (“Asco”) for $650.0 in cash, subject to certain customary closing adjustments, including foreign currency adjustments. As such, movements in the Euro exchange rates could cause the purchase price to fluctuate, affecting our cash flows.

To reduce the Company's exposure to currency exchange rate fluctuations, the Company entered into foreign currency forward contracts. The objective of these contracts is to minimize the impact of currency exchange rate movements on the Company's cash flows, however the Company has not designated these forward contracts as a hedge and has not applied hedge accounting to them. During the second quarter of 2018, to reduce the Euro exchange rate exposure of the purchase of Asco, the Company entered into a foreign currency forward contract in the amount of $580.0; this foreign currency forward contract was settled in the third quarter of 2018. Additionally, during the third quarter of 2018, to reduce the Euro exchange rate exposure of the purchase of Asco, the Company entered into a foreign currency forward contract in the amount of $568.3. The fair value of the foreign currency forward contract, using Level 2 inputs, was a liability of $6.0 as of September 27, 2018. The Company recorded a net gain related to foreign currency forward contract activity of $0.8 for the three months ended September 27, 2018 and a net loss of $20.7 for the nine months ended September 27, 2018.