Stock-Based Compensation - Additional Information (Details) - USD ($)	1 Months Ended				12 Months Ended
	May 31, 2016	Aug. 31, 2015	Jul. 31, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Aug. 31, 2014
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock, shares outstanding					104,321,000	101,282,000
Common stock reserved for issuance					30,595,000	27,307,000
Unvested exercisable shares					276,660	517,285
Unvested exercisable shares, vesting period					2 years 2 months 12 days
Unvested options exercised					0	0
Unvested options subject to repurchase, outstanding					0	0
Weighted-average grant-date fair value of stock options granted					$ 2.26	$ 4.56	$ 3.72
Total intrinsic value of options exercised					$ 6,300,000	$ 8,100,000	$ 4,800,000
Total fair value of options vested					9,800,000	9,100,000	3,900,000
Compensation expense recognized					18,723,000	15,823,000	9,218,000
Total unrecognized compensation cost					$ 29,400,000	$ 20,900,000
Weighted-average period of recognition					2 years 7 months 6 days	2 years 9 months 18 days
Internal Use Software Development
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Capitalized stock based compensation expense					$ 100,000	$ 200,000	$ 100,000
Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for issuance					4,106,000	1,506,000
Stock option plan, number of shares granted					3,363,000	808,000	947,342
Vesting starting period					2014-08
Stock option plan, number of additional shares available for grant							372,342
Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for issuance					12,897,000	12,795,000
Outstanding stock options					154,000
Performance-based Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Compensation expense recognized					$ 1,200,000	$ 800,000
Expire in August 2017 | Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expiration period of RSUs					2017-08
Expire in September 2017 | Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expiration period of RSUs					2017-09
Expire in September 2019 | Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option plan, number of shares granted							575,000
Expiration period of RSUs					2019-09
MEC 2009 Stock Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock, shares outstanding					524,355
2013 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Additional common stock shares reserved for issuance				3,000,000
Common stock reserved for issuance				4,500,000
Stock options vesting period				4 years
Stock option plan, number of shares granted					0
2013 Equity Incentive Plan | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for issuance				8,044,829
Stock options granted, expiration period				10 years
2013 Equity Incentive Plan | End of One Year
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting award percentage				25.00%
2013 Equity Incentive Plan | Monthly Over the Remaining Three Years
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting award percentage				75.00%
2014 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for issuance			1,197,342					947,342
2014 Equity Incentive Plan | Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option plan, number of shares granted			1,197,342
2015 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for issuance			11,400,000		11,081,000	12,006,000
Stock options vesting period			4 years
Minimum annual automatic increase included in common stock reserved for future issuance as of first day of each fiscal year			10,000,000
Minimum percentage of annual automatic increase included in common stock reserved for future issuance as of last day of immediately preceding fiscal year			4.00%
Terms of shares available for issuance					The automatic increase of the number of shares available for issuance under the 2015 Plan is equal to the least of 10 million shares, 4% of the outstanding shares of common stock as of the last day of our immediately preceding fiscal year or such other amount as the Board of Directors may determine.
Additional common stock shares reserved for issuance	4,051,282
2015 Equity Incentive Plan | Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock options vesting period			4 years
Stock option plan, number of shares granted						250,000
Outstanding RSUs					470,000
2015 Equity Incentive Plan | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for issuance			15,439,334
Stock options granted, expiration period			10 years
2015 Equity Incentive Plan | End of One Year
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting award percentage			25.00%
2015 Equity Incentive Plan | End of One Year | Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting award percentage			25.00%
2015 Equity Incentive Plan | Monthly Over the Remaining Three Years
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting award percentage			75.00%
2015 Equity Incentive Plan | Quarterly Over the Remaining Three Years | Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting award percentage			75.00%
Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for issuance		1,000,000
Minimum annual automatic increase included in common stock reserved for future issuance as of first day of each fiscal year		5,000,000
Minimum percentage of annual automatic increase included in common stock reserved for future issuance as of last day of immediately preceding fiscal year		2.00%
Terms of shares available for issuance					The ESPP provides for an automatic increase of the number of shares available for issuance under the ESPP on the first day of each fiscal year beginning on January 1, 2016, equal to the least of 5 million shares, 2% of the outstanding shares of our common stock on the last day of the immediately preceding fiscal year, or such other amount as may be determined by the Board of Directors.
Additional common stock shares reserved for issuance		2,025,641
Maximum deductible fair market value of shares available for employee to purchase per calendar year		$ 25,000
Maximum percentage in payroll deductions to acquire shares of common stock		15.00%
Maximum number of shares available for employee to purchase per offering period		2,000
Term of offering period					Eligible employees are offered shares bi-annually through two six month offering periods, which begin on the first trading day on or after May 15 and November 15 of each year.