Summary of Business and Significant Accounting Policies - Schedule of Unaudited Condensed Consolidated Statements of Comprehensive Income (Detail) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended			9 Months Ended
		Oct. 31, 2018	Oct. 31, 2017		Oct. 31, 2018	Oct. 31, 2017
Revenues:
Subscription services		$ 224,731	$ 177,008	[1]	$ 629,887	$ 504,575	[1]
Operating expenses:
Sales and marketing	[2]	37,699	31,892	[1]	110,306	94,103	[1]
Operating income		63,094	42,495	[1]	159,868	119,425	[1]
Provision for income taxes		3,615	8,929	[1]	11,274	13,710	[1]
Net income		$ 64,085	$ 34,925	[1]	$ 158,681	$ 110,523	[1]
Net income per share attributable to Class A and Class B common stockholders:
Basic		$ 0.44	$ 0.25	[1]	$ 1.10	$ 0.79	[1]
Diluted		$ 0.41	$ 0.23	[1]	$ 1.02	$ 0.72	[1]
Subscription services [Member]
Revenues:
Subscription services		$ 178,214	$ 142,802	[1]	$ 503,809	$ 407,483	[1]
As Reported [member] | Topic 606 [Member]
Operating expenses:
Sales and marketing			31,856			93,683
Operating income			41,668			115,905
Provision for income taxes			8,635			12,454
Net income			$ 34,393			$ 108,260
Net income per share attributable to Class A and Class B common stockholders:
Basic			$ 0.24			$ 0.77
Diluted			$ 0.22			$ 0.71
As Reported [member] | Subscription services [Member] | Topic 606 [Member]
Revenues:
Subscription services			$ 141,943			$ 403,560
Adjustments [Member] | Topic 606 [Member]
Operating expenses:
Sales and marketing	[3]		36			420
Operating income	[3]		827			3,520
Provision for income taxes	[3]		294			1,256
Net income	[3]		$ 532			$ 2,263
Net income per share attributable to Class A and Class B common stockholders:
Basic	[3]		$ 0.01			$ 0.02
Diluted	[3]					$ 0.01
Adjustments [Member] | Subscription services [Member] | Topic 606 [Member]
Revenues:
Subscription services	[3]		$ 859			$ 3,923

[1] See note 1 of the notes to the condensed consolidated financial statements for a summary of adjustments.

[2] Includes stock-based compensation as follows:  Cost of revenues: Cost of subscription services $405 $377 $1,166 $1,095 Cost of professional services and other 2,782 2,288 7,767 6,110 Research and development 5,820 4,765 16,282 12,916 Sales and marketing 4,825 4,130 13,743 12,150 General and administrative 6,086 2,458 17,689 6,915 Total stock-based compensation $19,918 $14,018 $56,647 $39,186

[3] Adjusted to reflect the adoption of ASU 2014-09, “Revenue from Contracts with Customers (Topic 606).”