Subsequent Events	12 Months Ended
Jan. 31, 2018
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events On February 22, 2018, the Company priced its private offering of $300.0 million aggregate principal amount of Convertible Senior Notes due 2023 (the “Initial Notes”). On February 23, 2018, the initial purchasers in the offering of the Notes exercised their option to purchase an additional $45.0 million aggregate principal amount of the Notes (the “Additional Notes” and together with the “Initial Notes”, the “Notes”), bringing the total aggregate principal amount of Notes to $345.0 million. On February 27, 2018, the Company received approximately $334.0 million in net proceeds from the offering of the Notes, after deducting the initial purchasers’ discount and commissions and estimated offering expenses payable by the Company. The Company used an aggregate amount of $80.0 million of the net proceeds from the sale of the Notes to purchase the Note Hedge Transactions (as defined below), which was partially offset by proceeds of $52.4 million received from the Warrant Transactions (as defined below). The Notes are senior, unsecured obligations of the Company and bear interest at a rate of 0.25% per year. Interest is payable semi-annually in arrears on February 15 and August 15 of each year, beginning on August 15, 2018. The Notes will mature on February 15, 2023, unless earlier repurchased or converted. The Company may not redeem the Notes prior to their maturity. The Notes are convertible into shares of Company’s Class A common stock at an initial conversion rate of 20.6795 shares of Class A common stock per $1,000 principal amount, which is equal to an initial conversion price of approximately $48.36 per share of Class A common stock, subject to adjustment. Prior to October 15, 2022, the Notes will be convertible at the option of holders during certain periods, upon satisfaction of certain limited conditions. Thereafter, the Notes will be convertible at any time until the close of business on the second scheduled trading day immediately preceding the maturity date. Upon conversion, the Notes may be settled in shares of the Company’s Class A common stock, cash or a combination of cash and shares of the Company’s Class A common stock, at the Company’s election. Holders of the Notes will have the right to require the Company to repurchase all or a portion of their Notes upon the occurrence of a fundamental change (as defined in the indenture governing the Notes) at a purchase price of 100% of their principal amount plus any accrued and unpaid interest. In connection with the pricing of the Notes, the Company entered into convertible note hedge transactions (the "Note Hedge Transactions") with some of the initial purchasers of the Notes and/or their respective affiliates (the "Option Counterparties"). The Note Hedge Transactions are purchased call options containing a strike price equal to the initial conversion price of the Notes and an expiration date commensurate with the maturity date of the Notes. The Note Hedge Transactions are expected generally to reduce the potential dilution to the Class A common stock and/or offset the potential cash payments that the Company could be required to make in excess of the principal amount upon conversion of any Notes. The Company also entered into separate warrant transactions (the "Warrant Transactions") with the Option Counterparties pursuant to which the Company sold warrants for the purchase of the Company’s Class A common stock. These warrants will expire on May 15, 2023. The Warrant Transactions could separately have a dilutive effect to the extent that the market price per share of the Company’s Class A common stock exceeds the strike price of the warrants unless, subject to the terms of the Warrant Transactions, the Company elects to cash settle the warrants. The strike price of the warrants will initially be $68.06 per share, which represents a premium of 90.00% above the closing sale price of the Company’s Class A common stock on February 22, 2018, and is subject to certain adjustments under the terms of the Warrant Transactions.

Subsequent Events

On February 22, 2018, the Company priced its private offering of $300.0 million aggregate principal amount of Convertible Senior Notes due 2023 (the “Initial Notes”). On February 23, 2018, the initial purchasers in the offering of the Notes exercised their option to purchase an additional $45.0 million aggregate principal amount of the Notes (the “Additional Notes” and together with the “Initial Notes”, the “Notes”), bringing the total aggregate principal amount of Notes to $345.0 million. On February 27, 2018, the Company received approximately $334.0 million in net proceeds from the offering of the Notes, after deducting the initial purchasers’ discount and commissions and estimated offering expenses payable by the Company. The Company used an aggregate amount of $80.0 million of the net proceeds from the sale of the Notes to purchase the Note Hedge Transactions (as defined below), which was partially offset by proceeds of $52.4 million received from the Warrant Transactions (as defined below).

The Notes are senior, unsecured obligations of the Company and bear interest at a rate of 0.25% per year. Interest is payable semi-annually in arrears on February 15 and August 15 of each year, beginning on August 15, 2018. The Notes will mature on February 15, 2023, unless earlier repurchased or converted. The Company may not redeem the Notes prior to their maturity. The Notes are convertible into shares of Company’s Class A common stock at an initial conversion rate of 20.6795 shares of Class A common stock per $1,000 principal amount, which is equal to an initial conversion price of approximately $48.36 per share of Class A common stock, subject to adjustment. Prior to October 15, 2022, the Notes will be convertible at the option of holders during certain periods, upon satisfaction of certain limited conditions. Thereafter, the Notes will be convertible at any time until the close of business on the second scheduled trading day immediately preceding the maturity date. Upon conversion, the Notes may be settled in shares of the Company’s Class A common stock, cash or a combination of cash and shares of the Company’s Class A common stock, at the Company’s election. Holders of the Notes will have the right to require the Company to repurchase all or a portion of their Notes upon the occurrence of a fundamental change (as defined in the indenture governing the Notes) at a purchase price of 100% of their principal amount plus any accrued and unpaid interest.

In connection with the pricing of the Notes, the Company entered into convertible note hedge transactions (the "Note Hedge Transactions") with some of the initial purchasers of the Notes and/or their respective affiliates (the "Option Counterparties"). The Note Hedge Transactions are purchased call options containing a strike price equal to the initial conversion price of the Notes and an expiration date commensurate with the maturity date of the Notes. The Note Hedge Transactions are expected generally to reduce the potential dilution to the Class A common stock and/or offset the potential cash payments that the Company could be required to make in excess of the principal amount upon conversion of any Notes.

The Company also entered into separate warrant transactions (the "Warrant Transactions") with the Option Counterparties pursuant to which the Company sold warrants for the purchase of the Company’s Class A common stock. These warrants will expire on May 15, 2023. The Warrant Transactions could separately have a dilutive effect to the extent that the market price per share of the Company’s Class A common stock exceeds the strike price of the warrants unless, subject to the terms of the Warrant Transactions, the Company elects to cash settle the warrants. The strike price of the warrants will initially be $68.06 per share, which represents a premium of 90.00% above the closing sale price of the Company’s Class A common stock on February 22, 2018, and is subject to certain adjustments under the terms of the Warrant Transactions.