Debt - Senior Credit Agreement (Details)		3 Months Ended	6 Months Ended	12 Months Ended
	Sep. 15, 2015 USD ($)	Jul. 27, 2019 USD ($)	Jul. 27, 2019 USD ($)	Jan. 26, 2019 USD ($)	Oct. 19, 2018 USD ($)
Line of Credit Facility [Line Items]
Letters of credit outstanding amount		$ 52,300,000	$ 52,300,000	$ 48,600,000
Additional borrowing availability		276,500,000	276,500,000	412,900,000
Standby Letters of Credit
Line of Credit Facility [Line Items]
Line of credit maximum borrowing capacity					$ 200,000,000.0
Letters of credit outstanding amount		52,300,000	52,300,000	$ 48,600,000
Incremental Facility, Minimum
Line of Credit Facility [Line Items]
Debt instrument, face amount	$ 350,000,000.0
Credit Agreement - Term Loan (matures April 2020)
Line of Credit Facility [Line Items]
Line of credit maximum borrowing capacity					450,000,000.0
Debt instrument, covenant compliance, consolidated leverage ratio, maximum	2.25
Unrestricted cash and cash equivalents threshold		$ 50,000,000.0	$ 50,000,000.0
Credit Agreement - Revolving facility (matures April 2020)
Line of Credit Facility [Line Items]
Line of credit maximum borrowing capacity	$ 450,000,000.0				$ 750,000,000.0
Unutilized commitment fee (in percent)			0.35%	0.35%
Minimum
Line of Credit Facility [Line Items]
Debt instrument, covenant compliance, consolidated leverage ratio, maximum		3.50
Debt instrument, covenant compliance, consolidated interest coverage ratio, maximum		3.00
Minimum | Standby Letters of Credit
Line of Credit Facility [Line Items]
Unutilized commitment fee (in percent)			1.25%
Minimum | Credit Agreement - Revolving facility (matures April 2020)
Line of Credit Facility [Line Items]
Unutilized commitment fee (in percent)			0.20%
Maximum
Line of Credit Facility [Line Items]
Debt instrument, covenant compliance, consolidated leverage ratio, maximum		1.00
Debt instrument, covenant compliance, consolidated interest coverage ratio, maximum		1.00
Maximum | Standby Letters of Credit
Line of Credit Facility [Line Items]
Unutilized commitment fee (in percent)			2.00%
Maximum | Credit Agreement - Revolving facility (matures April 2020)
Line of Credit Facility [Line Items]
Unutilized commitment fee (in percent)			0.40%
0.75% Convertible Senior Notes Due 2021
Line of Credit Facility [Line Items]
Debt instrument, face amount	$ 485,000,000.0	$ 485,000,000	$ 485,000,000	$ 485,000,000
Outstanding debt threshold		250,000,000.0	250,000,000.0
Credit agreement liquidity requirement		$ 150,000,000.0	$ 150,000,000.0