Debt (Details Textual) - USD ($) shares in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jun. 06, 2016
Debt Instrument [Line Items]
Treasury Stock, Shares, Acquired	0.8	9.3	14.2
Optional Revolver Commitment	$ 750,000,000.0
2018 Amended Restated Credit Agreement [Member]
Debt Instrument [Line Items]
Borrowing capacity under the revolving credit facility	$ 1,256,000,000.0
Amended and Restated Credit Agreement Due 2021 [Member]
Debt Instrument [Line Items]
Level 1 Commitment Fee	0.125%
Level 2 Commitment Fee	0.15%
Level 3 Commitment Fee	0.20%
Level 4 Commitment Fee	0.25%
Level 1 Letter Of Credit Fee	1.125%
Level 2 Letter Of Credit Fee	1.25%
Level 3 Letter Of Credit Fee	1.375%
Level 4 Letter Of Credit Fee	1.625%
Level 1 Margin On Libor Borrowing On Revolving Loan	1.125%
Level 2 Margin On Libor Borrowing On Revolving Loan	1.25%
Level 3 Margin On Libor Borrowing On Revolving Loan	1.375%
Level 4 Margin On Libor Borrowing Revolving Loan	1.625%
Level 1 Margin On Alternate Base Rate Borrowing On Revolving Loan	0.125%
Level 2 Margin On Alternate Base Rate Borrowing On Revolving Loan	0.25%
Level 3 Margin On Alternate Base Rate Borrowing On Revolving Loan	0.375%
Level 4 Margin On Alternate Base Rate Revolving Loan	0.625%
Level 5 Commitment Fee	0.30%
Level 5 Letter Of Credit Fee	1.875%
Level 5 Margin On Libor Borrowing Revolving Loan	1.875%
Level 5 Margin On Alternate Base Rate Revolving Loan	0.875%
Senior Unsecured Notes Due 2022 [Member]
Debt Instrument [Line Items]
Extinguishment of Debt, Amount	$ 300,000,000.0
Gains (Losses) on Extinguishment of Debt	(13,200,000)
Incremental Tender Amount	97,400,000
Debt Instrument, Repurchase Amount	202,600,000
Senior Unsecured Notes Due 2026 [Member]
Debt Instrument [Line Items]
Secured Long-term Debt, Noncurrent		$ 297,500,000
Debt Instrument, Face Amount	$ 300,000,000.0
Fixed interest rate	3.85%
Senior Notes, Current
Senior Notes, Noncurrent	297,800,000
2018 Revolver [Member]
Debt Instrument [Line Items]
Borrowing capacity under the revolving credit facility	800,000,000.0
Senior Notes, Current	0	0
Senior Notes, Noncurrent	800,000,000.0	0
2018 Term Loan A [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	206,000,000.0
Delayed Draw Term Loan [Member]
Debt Instrument [Line Items]
Borrowing capacity under the revolving credit facility	$ 250,000,000.0
2018 Revolver, 2018 Term Loan, Delayed Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate Terms	Each of the Revolver, the Term Loan and the Delayed Draw Term Loan matures July 12, 2023, and bears interest, at Spirit’s option, at either LIBOR plus 1.375% or a defined “base rate” plus 0.375%, subject to adjustment to between LIBOR plus 1.125% and LIBOR plus 1.875% (or between base rate plus 0.125% and base rate plus 0.875%, as applicable) based on changes to Spirit’s senior unsecured debt rating provided by Standard & Poor’s Financial Services LLC and/or Moody’s Investors Service, Inc.
Senior unsecured term loan A [Member]
Debt Instrument [Line Items]
Secured Long-term Debt, Noncurrent		182,000,000.0
Quarterly principal repayment from September 2011 through May 2017 until entirely repaid	$ 2,600,000
Senior Notes, Current	22,800,000
Senior Notes, Noncurrent	415,700,000
Senior Unsecured Notes Due 2021 [Member] [Domain]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	300,000,000.0
Senior Notes, Current		0
Debt Instrument, Interest Rate Terms	The Floating Rate Notes bear interest at a rate per annum equal to three-month LIBOR, as determined in the case of the initial interest period, on May 25, 2018, and thereafter at the beginning of each quarterly period as described herein, plus 80 basis points and mature on June 15, 2021. Interest on the Floating Rate Notes is payable on March 15, June 15, September 15 and December 15 of each year, beginning on September 15, 2018.
Senior Notes, Noncurrent	$ 299,100,000	298,500,000
Senior Unsecured Notes Due 2023 [Member] [Domain]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	300,000,000.0
Fixed interest rate				3.95%
Senior Notes, Current		0
Debt Instrument, Interest Rate Terms	The 2023 Notes bear interest at a rate of 3.950% per annum and mature on June 15, 2023.
Senior Notes, Noncurrent	$ 298,300,000	297,900,000
Senior Unsecured Notes Due 2028 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 700,000,000.0
Fixed interest rate	4.60%
Senior Notes, Current		0
Debt Instrument, Interest Rate Terms	The 2028 Notes bear interest at a rate of 4.600% per annum and mature on June 15, 2028.
Senior Notes, Noncurrent	$ 694,100,000	$ 693,500,000
Senior Unsecured Notes due 2023 and 2028 [Member]
Debt Instrument [Line Items]
Debt Instrument, Payment Terms	Interest on the 2023 Notes and 2028 Notes is payable on June 15 and December 15 of each year, beginning on December 15, 2018.