Income taxes	3 Months Ended
Apr. 30, 2019
Income Tax Disclosure [Abstract]
Income taxes	Income taxes The Company follows FASB Accounting Standards Codification 740-270, Income Taxes - Interim Reporting, for the computation and presentation of its interim period tax provision. Accordingly, management estimated the effective annual tax rate and applied this rate to the year-to-date pre-tax book income to determine the interim provision for income taxes. For the three months ended April 30, 2019, the Company recorded income tax expense of $9.5 million. This resulted in an effective income tax expense rate of 18.4% for the three months ended April 30, 2019, compared with an effective income tax benefit rate of 9.9% for the three months ended April 30, 2018. For the three months ended April 30, 2019 and 2018, the net impact of discrete tax items caused a 4.5 and 31.8 percentage point decrease, respectively, to the effective income tax rate primarily due to the excess tax benefit on stock-based compensation expense recognized in the provision for income taxes in the condensed consolidated statements of operations and comprehensive income. The increase in the effective income tax rate from the same period last year is primarily due to a decrease in excess tax benefits on stock-based compensation expense recognized in the provision for income taxes relative to pre-tax book income. As of April 30, 2019 and January 31, 2019, the Company’s total gross unrecognized tax benefit was $1.9 million and $1.7 million, respectively. Certain unrecognized tax benefits have been netted against their related deferred tax assets; therefore, no unrecognized tax benefit has been recorded as of April 30, 2019 and January 31, 2019. If recognized, $1.7 million of the total gross unrecognized tax benefits would affect the Company's effective tax rate as of April 30, 2019. The Company files income tax returns with U.S. federal and state taxing jurisdictions and is not currently under examination with any jurisdiction. The Company remains subject to examination by federal and various state taxing jurisdictions for tax years after 2003.

Income taxes

The Company follows FASB Accounting Standards Codification 740-270, Income Taxes - Interim Reporting, for the computation and presentation of its interim period tax provision. Accordingly, management estimated the effective annual tax rate and applied this rate to the year-to-date pre-tax book income to determine the interim provision for income taxes. For the three months ended April 30, 2019, the Company recorded income tax expense of $9.5 million. This resulted in an effective income tax expense rate of 18.4% for the three months ended April 30, 2019, compared with an effective income tax benefit rate of 9.9% for the three months ended April 30, 2018. For the three months ended April 30, 2019 and 2018, the net impact of discrete tax items caused a 4.5 and 31.8 percentage point decrease, respectively, to the effective income tax rate primarily due to the excess tax benefit on stock-based compensation expense recognized in the provision for income taxes in the condensed consolidated statements of operations and comprehensive income. The increase in the effective income tax rate from the same period last year is primarily due to a decrease in excess tax benefits on stock-based compensation expense recognized in the provision for income taxes relative to pre-tax book income.

As of April 30, 2019 and January 31, 2019, the Company’s total gross unrecognized tax benefit was $1.9 million and $1.7 million, respectively. Certain unrecognized tax benefits have been netted against their related deferred tax assets; therefore, no unrecognized tax benefit has been recorded as of April 30, 2019 and January 31, 2019. If recognized, $1.7 million of the total gross unrecognized tax benefits would affect the Company's effective tax rate as of April 30, 2019.

The Company files income tax returns with U.S. federal and state taxing jurisdictions and is not currently under examination with any jurisdiction. The Company remains subject to examination by federal and various state taxing jurisdictions for tax years after 2003.