Description of Business and Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	12 Months Ended			85 Months Ended	1 Months Ended
	Mar. 31, 2015 Segment LetterOfCredit	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2015 LetterOfCredit	Dec. 31, 2014	Apr. 30, 2014
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Company incorporation date	Feb. 20, 2008
Entity Incorporation, State Name	Delaware
Proceeds from sale of common stock, net of underwriters' discounts and commissions	$ 119,924,000
Number of reportable segments	1
Cash and cash equivalents, original maturity term	Three months or less
Number of letters of Credit, pledged as collateral	2			2
Other-than-temporarily impaired investments	0
Short-term investments	95,503,000	0		95,503,000
Gross value of capitalized internal use software	10,000,000	5,500,000	3,000,000	10,000,000
Stock-based compensation costs	1,000,000	300,000	100,000
Amortization expense	3,900,000	2,100,000	1,100,000
Net book value of capitalized software	12,600,000	6,500,000		12,600,000
Deferred offering costs	0			0
Impairment of long-lived assets	0	0	0
Goodwill impairment				0
Other Noncurrent Assets [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Deferred offering costs		200,000
Minimum [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Revenue recognition, contract term	1 month
Maximum [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Revenue recognition, contract term	12 months
Computers and software [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Property plant and equipment estimated useful life	2 years
Other Office Equipment and Site-related Computer Hardware [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Property plant and equipment estimated useful life	3 years
Furniture and Fixtures [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Property plant and equipment estimated useful life	5 years
Leasehold Improvements [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Property plant and equipment, estimated useful life	The shorter of the lease-term or the estimated useful life of the related asset.
Capitalized Software Development Costs [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Property plant and equipment estimated useful life	3 years
Common Stock [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Number of common stock shares issued upon conversion of convertible preferred stock					24,885,778
Accounts Receivable [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Number of customers	1	0
Revenue [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Number of customers	0	0	0
Series F Convertible Preferred Stock [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Common stock shares issued, price per share						$ 28.93
Convertible preferred stock conversion rate					1.02	1
Series A Through E Preferred Stock [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Convertible preferred stock conversion rate					1
Convertible Preferred Stock [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Number of convertible preferred stock shares converted					24,813,343
Credit Concentration Risk [Member] | Accounts Receivable [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Concentration of risk, percentage	12.00%	10.00%
Credit Concentration Risk [Member] | Revenue [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Concentration of risk, percentage	10.00%	10.00%	10.00%
Initial Public Offering [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Common stock shares issued					5,750,000
Proceeds from sale of common stock, net of underwriters' discounts and commissions					123,000,000
Common stock shares issued, price per share					23.00	$ 23.00
Offering expenses					3,100,000
Initial Public Offering [Member] | Series F Convertible Preferred Stock [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Convertible preferred stock conversion rate						1.02
Sales and Marketing [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Advertising Expense	$ 25,100,000	$ 22,400,000	$ 10,000,000