Share-Based Compensation - Narrative (Details) $ / shares in Units, $ in Millions						3 Months Ended	12 Months Ended
	Jan. 08, 2021 shares	Mar. 05, 2019 $ / shares shares	Apr. 27, 2018 shares	Oct. 05, 2016 shares	Feb. 26, 2014	Apr. 29, 2018 USD ($) employee shares	Jan. 31, 2021 USD ($) $ / shares shares	Jan. 26, 2020 USD ($) shares	Jan. 27, 2019 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized per the equity incentive plan							17,031,653
Aggregate unrecognized compensation for stock options | $							$ 0.9
Number of employees affected by modification of awards | employee						8
Number of shares affected (in shares)						159,000
Additional compensation cost | $						$ 2.8
Maximum number of shares subject to purchase under warrants				1,086,957
Number of shares underlying the Warrant that vested			586,956
Warrant vesting costs | $									$ 21.5
Warrant vesting costs due to acceleration | $									$ 15.9
Number of securities called by warrants (in shares)									869,565
Options granted (in dollars per share) | $ / shares									$ 14.53
Options granted (in shares)							0	0
Share Price | $ / shares							$ 70.95
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Period over which aggregate unrecognized compensation will be recognized							1 year 3 months 18 days
Performance-based RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of award that will vest upon satisfaction of performance condition									180.80%
Total number of unvested shares (in shares)							0
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value | $								$ 9.3
Market performance RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate unrecognized compensation | $							$ 4.7
Period over which aggregate unrecognized compensation will be recognized							1 year 4 months 24 days
Weighted average fair value units granted (in dollars per share) | $ / shares							$ 32.66
Stock units granted (in shares)							137,224	266,000	200,442
Total number of unvested shares (in shares)							203,000	257,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period							18,682
Employee stock unit awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period							4 years
Aggregate unrecognized compensation for stock options | $							$ 82.3
Period over which aggregate unrecognized compensation will be recognized							2 years 4 months 24 days
Weighted average fair value units granted (in dollars per share) | $ / shares							$ 56.28
Stock units granted (in shares)							909,000
Total number of unvested shares (in shares)							2,059,000	2,102,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period							841,000
Minimum | Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period							3 years
Maximum | Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period							4 years
Contractual term of equity share options							10 years
Subject to share settlement | Performance-based RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period								187,116
Subject to cash settlement | Performance-based RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period								187,116
Subject to cash settlement | Non-employee director stock unit awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period							1 year
Tranche One | Market performance RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average fair value units granted (in dollars per share) | $ / shares							$ 29.04
Tranche Two | Market performance RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average fair value units granted (in dollars per share) | $ / shares							32.94
Tranche Three | Market performance RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average fair value units granted (in dollars per share) | $ / shares							$ 35.99
Vesting January 31, 2021 | Market performance RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-Based Compensation Arrangement By Share-Based Payment Award, Equity Instruments Other Than Options, Expected To Vest							178,978
Chief Executive Officer | Market performance RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate unrecognized compensation | $							$ 0.7
Period over which aggregate unrecognized compensation will be recognized							2 months 12 days
Stock units granted (in shares)		320,000
Chief Executive Officer | Tranche One | Market performance RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation, terms of award					The award is eligible to vest during the period commencing February 26, 2014 and ending February 26, 2019 (the “Performance Period”) as follows: 30% of the restricted stock units covered by the award will vest if, during any consecutive 120 calendar day period that commences and ends during the Performance Period, the average per-share closing price of the Company’s common stock equals or exceeds $35.00 (“Tranche 1”) and the award will vest in full if, during any consecutive 120 calendar day period that commences and ends during the Performance Period, the average per-share closing price of the Company’s common stock equals or exceeds $40.00 (“Tranche 2”). The award will also vest if a majority change in control of the Company occurs during the Performance Period and, in connection with such event, the Company’s stockholders become entitled to receive per-share consideration having a value equal to or greater than $40.00.
Percentage of award that will vest upon satisfaction of performance condition		30.00%
Award performance period		30 days
Minimum closing share price used to determine market condition (usd per share) | $ / shares		$ 71.00
Weighted average fair value units granted (in dollars per share) | $ / shares							$ 44.32
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period	96,000
Chief Executive Officer | Tranche Two | Market performance RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of award that will vest upon satisfaction of performance condition					100.00%
Award performance period		30 days
Minimum closing share price used to determine market condition (usd per share) | $ / shares		$ 95.00
Weighted average fair value units granted (in dollars per share) | $ / shares							$ 33.19
Chief Executive Officer | Tranche Three | Market performance RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of award that will vest upon satisfaction of performance condition		30.00%
Chief Executive Officer | Tranche Three | Minimum | Market performance RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Minimum closing share price used to determine market condition (usd per share) | $ / shares		$ 71.00
Chief Executive Officer | Tranche Three | Maximum | Market performance RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Minimum closing share price used to determine market condition (usd per share) | $ / shares		$ 95.00
Non-employee director stock unit awards | Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period							1 year
Share-based compensation liability, long-term | $							$ 14.0
Weighted average fair value units granted (in dollars per share) | $ / shares							$ 51.52
Stock units granted (in shares)							28,000
Total number of unvested shares (in shares)							28,000	26,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested and Unsettled in Period							188,739
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period							26,000
Non-employee director stock unit awards | Subject to share settlement | Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock units granted (in shares)							13,000
Total number of unvested shares (in shares)							13,000	12,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period							12,000
Non-employee director stock unit awards | Subject to cash settlement | Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock units granted (in shares)							15,000
Total number of unvested shares (in shares)							15,000	14,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period							14,000