Debt (Narrative) (Details) - USD ($)		9 Months Ended	12 Months Ended
	Jan. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 15, 2017	Jul. 21, 2017	Nov. 14, 2016	Jun. 17, 2016	Sep. 24, 2015
Line of Credit Facility [Line Items]
Debt Instrument, Maturity Date			Jul. 09, 2019
Debt Instrument Maturities Quarterly Repayments of Principal										$ 3,800,000
Issuance in letters of credit			$ 30,000,000
Outstanding letters of credit			17,400,000
Loss from debt extinguishment			15,876,000	$ 0	$ 0
Revolving credit facility
Line of Credit Facility [Line Items]
Revolving credit facility								$ 250,000,000.0	$ 300,000,000	400,000,000
Term Loan Facility Maturing [Member]
Line of Credit Facility [Line Items]
Term loan										$ 300,000,000
Subsequent Event
Line of Credit Facility [Line Items]
Proceeds from Issuance or Sale of Equity	$ 52,500,000
Subsequent Event | London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate	2.25%
Subsequent Event | Base Rate
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.25%
ABL Facility | Revolving credit facility
Line of Credit Facility [Line Items]
Revolving credit facility			141,700,000			$ 15,000,000	$ 200,000,000
ABL Facility | Bridge Loan
Line of Credit Facility [Line Items]
Revolving credit facility							20,000,000
ABL Facility | Letter of Credit
Line of Credit Facility [Line Items]
Revolving credit facility							30,000,000
ABL Facility | Term Loan Facility
Line of Credit Facility [Line Items]
Revolving credit facility			$ 56,800,000				56,800,000
ABL Facility | Asset-Based Facility
Line of Credit Facility [Line Items]
Revolving credit facility							$ 35,000,000
ABL Facility | Minimum | London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate			1.50%
ABL Facility | Minimum | Base Rate
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate			0.50%
ABL Facility | Maximum | London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate			2.25%
ABL Facility | Maximum | Base Rate
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate			1.25%
Senior Notes
Line of Credit Facility [Line Items]
Loss from debt extinguishment		$ 9,800,000