Financing Agreements (Narrative) (Details) - USD ($)		3 Months Ended			6 Months Ended		12 Months Ended
	May 01, 2019	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019	Sep. 30, 2019	Jun. 30, 2019
Debt Instrument [Line Items]
Payment of long-term debt					$ (25,100,000)	$ 100,000
Payment for Debt Extinguishment or Debt Prepayment Cost					(12,200,000)	0
Gain (Loss) on Extinguishment of Debt		$ 0		$ 0	(15,600,000)	$ 0
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Revolving credit facility, matures September 2021							$ 80,000,000.0
Securitization Program [Member]
Debt Instrument [Line Items]
Debt Instrument, Term	364 days
Aggregate value of debt	$ 110,000,000.0
Unsecured debenture interest rate								0.675%
Note Securitization Facility [Member]
Debt Instrument [Line Items]
Debt Instrument, Term	364 days
Aggregate value of debt	$ 90,000,000.0
Senior Secured Term Loan A [Member]
Debt Instrument [Line Items]
Long-term Debt, Maturities, Repayments of Principal in Year Three								$ 0
Maximum interest rate during period							0.00%
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Senior revolving credit facility, maximum borrowing amount		1,007.8			1,007.8
Current borrowing capacity under the facility							$ 1,112.8
Outstanding letters of credit		7,200,000			7,200,000		$ 7,200,000
Debtor-in-Possession Financing, Borrowings Outstanding		$ 185,000,000.0			$ 185,000,000.0
Senior Secured Credit Facilities [Member]
Debt Instrument [Line Items]
Maximum interest rate during period			2.30%
Senior Unsecured 5.75% Notes due on September 1, 2023 [Member]
Debt Instrument [Line Items]
Unsecured debenture interest rate		5.75%			5.75%			5.75%
Payment for Debt Extinguishment or Debt Prepayment Cost		$ (12,200,000)
Gain (Loss) on Extinguishment of Debt		15,600,000
Write off of Deferred Debt Issuance Cost		$ 3,400,000
Senior Unsecured 5.00% Notes due on February 14, 2025 [Member]
Debt Instrument [Line Items]
Unsecured debenture interest rate							5.00%
Senior Unsecured 4.375% Notes due September 2027 [Member]
Debt Instrument [Line Items]
Aggregate value of debt							$ 425,000,000.0
Unsecured debenture interest rate							4.375%
London Interbank Offered Rate (LIBOR) [Member] | Securitization Program [Member]
Debt Instrument [Line Items]
Unsecured debenture interest rate		0.80%			0.80%
London Interbank Offered Rate (LIBOR) [Member] | Note Securitization Facility [Member]
Debt Instrument [Line Items]
Unsecured debenture interest rate		0.90%			0.90%		100.00%