CONDENSED CONSOLIDATED STATEMENTS OF SHAREHOLDERS' (DEFICIT) EQUITY - USD ($) $ in Millions	Total	Cumulative Effect, Period Of Adoption, Adjustment	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated Deficit Cumulative Effect, Period Of Adoption, Adjustment	Accumulated Other Comprehensive Loss
Beginning balance (in shares) at Aug. 04, 2018			9,817,000
Beginning balance at Aug. 04, 2018	$ 798.5		$ 0.1	$ 1,090.1	$ (278.8)		$ (12.9)
Beginning balance (Accounting Standards Update 2014-09) at Aug. 04, 2018		$ 4.9				$ 4.9
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	5.9				5.9
Total other comprehensive income	(0.4)						(0.4)
Shares issued and equity grants made pursuant to stock-based compensation plans (in shares)			54,000
Shares issued and equity grants made pursuant to stock-based compensation plans	4.3			4.8	(0.5)
Ending balance (in shares) at Nov. 03, 2018			9,871,000
Ending balance at Nov. 03, 2018	813.2		$ 0.1	1,094.9	(268.5)		(13.3)
Beginning balance (in shares) at Aug. 04, 2018			9,817,000
Beginning balance at Aug. 04, 2018	798.5		$ 0.1	1,090.1	(278.8)		(12.9)
Beginning balance (Accounting Standards Update 2014-09) at Aug. 04, 2018		4.9				4.9
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(303.5)
Total other comprehensive income	(1.1)
Ending balance (in shares) at May. 04, 2019			9,890,000
Ending balance at May. 04, 2019	509.3		$ 0.1	1,101.2	(578.0)		(14.0)
Beginning balance (in shares) at Nov. 03, 2018			9,871,000
Beginning balance at Nov. 03, 2018	813.2		$ 0.1	1,094.9	(268.5)		(13.3)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(71.5)				(71.5)
Shares issued and equity grants made pursuant to stock-based compensation plans (in shares)			7,000
Shares issued and equity grants made pursuant to stock-based compensation plans	3.7			3.8	(0.1)
Ending balance (in shares) at Feb. 02, 2019			9,878,000
Ending balance at Feb. 02, 2019	745.4		$ 0.1	1,098.7	(340.1)		(13.3)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(237.9)				(237.9)
Total other comprehensive income	(0.7)						(0.7)
Shares issued and equity grants made pursuant to stock-based compensation plans (in shares)			12,000
Shares issued and equity grants made pursuant to stock-based compensation plans	2.5			2.5
Ending balance (in shares) at May. 04, 2019			9,890,000
Ending balance at May. 04, 2019	509.3		$ 0.1	1,101.2	(578.0)		(14.0)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accumulated deficit	(935.9)
Accumulated deficit | Accounting Standards Update 2016-02	$ (947.4)
Beginning balance (in shares) at Aug. 03, 2019	9,925,000		9,925,000
Beginning balance at Aug. 03, 2019	$ 151.0		$ 0.1	1,102.5	(935.9)		(15.7)
Beginning balance (Accounting Standards Update 2016-02) at Aug. 03, 2019		(11.5)				(11.5)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	31.7				31.7
Total other comprehensive income	0.2						0.2
Shares issued and equity grants made pursuant to stock-based compensation plans (in shares)			47,000
Shares issued and equity grants made pursuant to stock-based compensation plans	1.6			1.6
Ending balance (in shares) at Nov. 02, 2019			9,972,000
Ending balance at Nov. 02, 2019	$ 173.0		$ 0.1	1,104.1	(915.7)		(15.5)
Beginning balance (in shares) at Aug. 03, 2019	9,925,000		9,925,000
Beginning balance at Aug. 03, 2019	$ 151.0		$ 0.1	1,102.5	(935.9)		(15.7)
Beginning balance (Accounting Standards Update 2016-02) at Aug. 03, 2019		$ (11.5)				$ (11.5)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(709.2)
Total other comprehensive income	$ (4.4)
Ending balance (in shares) at May. 02, 2020	10,046,000		10,046,000
Ending balance at May. 02, 2020	$ (570.8)		$ 0.1	1,105.8	(1,656.6)		(20.1)
Beginning balance (in shares) at Nov. 02, 2019			9,972,000
Beginning balance at Nov. 02, 2019	173.0		$ 0.1	1,104.1	(915.7)		(15.5)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(97.4)				(97.4)
Total other comprehensive income	0.1						0.1
Shares issued and equity grants made pursuant to stock-based compensation plans (in shares)			14,000
Shares issued and equity grants made pursuant to stock-based compensation plans	0.9			0.9
Ending balance (in shares) at Feb. 01, 2020			9,986,000
Ending balance at Feb. 01, 2020	76.6		$ 0.1	1,105.0	(1,013.1)		(15.4)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(643.5)				(643.5)
Total other comprehensive income	(4.7)						(4.7)
Shares issued and equity grants made pursuant to stock-based compensation plans (in shares)			60,000
Shares issued and equity grants made pursuant to stock-based compensation plans	$ 0.8			0.8
Ending balance (in shares) at May. 02, 2020	10,046,000		10,046,000
Ending balance at May. 02, 2020	$ (570.8)		$ 0.1	$ 1,105.8	$ (1,656.6)		$ (20.1)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accumulated deficit	(1,656.6)
Accumulated deficit | Accounting Standards Update 2016-02	$ (11.5)