Stockholders' Equity - Additional Information (Details)						1 Months Ended	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 01, 2018 shares	Oct. 19, 2017 employee shares	Apr. 03, 2017 employee shares	Feb. 27, 2017 shares	Oct. 03, 2016 employee shares	Apr. 30, 2018	Jun. 30, 2019 USD ($) $ / shares shares	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) $ / shares shares	Jun. 30, 2018 USD ($) shares	Dec. 31, 2018 $ / shares shares	Jun. 14, 2019 USD ($)	Dec. 16, 2016 shares	Jun. 27, 2007 shares
Preferred Stock
Preferred stock, par value (in dollars per share) | $ / shares							$ 0.001		$ 0.001		$ 0.001
Preferred stock, shares authorized (in shares)							5,000,000		5,000,000		5,000,000
Preferred stock, shares issued (in shares)							0		0		0
Preferred stock, shares outstanding (in shares)							0		0		0
Common Stock
Common stock, par value (in dollars per share) | $ / shares							$ 0.001		$ 0.001		$ 0.001
Common stock, shares authorized (in shares)							100,000,000		100,000,000		100,000,000
Exercise of stock options (in shares)									157,334		1,079,496
Stock repurchase program, authorized amount | $												$ 30,000,000.0
Shares repurchased (in shares)							0		0
Stock-Based Compensation
Unrecognized compensation cost, stock options | $							$ 1,000,000		$ 1,000,000
Stock-based compensation expense | $							2,865,336	$ 2,090,870	$ 5,290,053	$ 4,259,795
Unvested RSAs
Common Stock
Issuance of common stock for vested RSAs (in shares)									1,372,723		1,591,662
Stock-Based Compensation
Vesting period									3 years
Unrecognized compensation cost, RSAs | $							16,900,000		$ 16,900,000
Unrecognized compensation cost, period of recognition									2 years 2 months 12 days
Unvested RSAs | Tranche 1
Stock-Based Compensation
Vesting period									1 year
Vesting percentage									33.00%
Unvested RSAs | Tranche 2
Stock-Based Compensation
Vesting period									1 year
Vesting percentage									33.00%
Unvested RSAs | Tranche 3
Stock-Based Compensation
Vesting period									1 year
Vesting percentage									33.00%
Performance shares
Stock-Based Compensation
Unrecognized compensation cost, RSAs | $							3,500,000		$ 3,500,000
Unrecognized compensation cost, period of recognition									2 years 6 months
Stock options
Stock-Based Compensation
Unrecognized compensation cost, period of recognition									9 months 18 days
2012 Omnibus Incentive Plan
Common Stock
Exercise of stock options (in shares)									106,903
Stock-Based Compensation
Shares reserved for issuance (in shares)	300,000												10,500,000
Stock-based compensation expense | $							300,000	400,000	$ 600,000	800,000
Intrinsic value of options exercised | $									$ 200,000	200,000
Options granted (in shares)									0
2012 Omnibus Incentive Plan | Unvested RSAs
Stock-Based Compensation
Vesting period									3 years
Expiration period									3 years
Stock-based compensation expense | $							400,000	1,100,000	$ 1,100,000	2,200,000
2012 Omnibus Incentive Plan | Performance shares
Stock-Based Compensation
Vesting period						3 years
Stock-based compensation expense | $							$ 100,000	100,000	$ 300,000	100,000
2018 Omnibus Incentive Plan
Stock-Based Compensation
Shares reserved for issuance (in shares)	8,800,000
Fungible ratio	1.4
Shares available for grant (in shares)							3,400,000		3,400,000
2018 Omnibus Incentive Plan | Unvested RSAs
Stock-Based Compensation
Vesting period									3 years
Expiration period									3 years
Stock-based compensation expense | $							$ 1,600,000	100,000	$ 2,500,000	100,000
2018 Omnibus Incentive Plan | Performance shares
Stock-Based Compensation
Stock-based compensation expense | $							200,000		$ 20,000
Amended and Restated 2006 Stock Incentive Plan
Stock-Based Compensation
Shares reserved for issuance (in shares)													2,100,000
2006 Stock Plan
Common Stock
Exercise of stock options (in shares)									23,764
Stock-Based Compensation
Shares reserved for issuance (in shares)														3,700,000
Intrinsic value of options exercised | $									$ 50,000	$ 0
Options granted (in shares)									0
The Amended and Restated 2016 Inducement Omnibus Incentive Plan
Common Stock
Exercise of stock options (in shares)									26,667	0
Stock-Based Compensation
Stock-based compensation expense | $							100,000	100,000	$ 200,000	$ 200,000
Intrinsic value of options exercised | $									$ 10,000
Options granted (in shares)									0
Additional shares authorized for issuance (in shares)				2,000,000
The Amended and Restated 2016 Inducement Omnibus Incentive Plan | Former Skout Employees
Stock-Based Compensation
Options granted (in shares)					355,000
The Amended and Restated 2016 Inducement Omnibus Incentive Plan | Unvested RSAs
Stock-Based Compensation
Vesting period									3 years
Expiration period									3 years
Stock-based compensation expense | $							$ 200,000	$ 300,000	$ 400,000	$ 700,000
Skout
Stock-Based Compensation
Number of former employees of acquiree | employee					25
If(we), Inc. | Unvested RSAs
Stock-Based Compensation
Number of former employees of acquiree | employee			83
Restricted stock awards granted (in shares)			717,500
If(we), Inc. | Stock options
Stock-Based Compensation
Options granted (in shares)			75,000
Lovoo, Inc. | Unvested RSAs
Stock-Based Compensation
Number of former employees of acquiree | employee		96
Restricted stock awards granted (in shares)		531,500
Minimum | 2012 Omnibus Incentive Plan | Performance shares
Stock-Based Compensation
Payout threshold range									33.00%
Minimum | 2018 Omnibus Incentive Plan | Performance shares
Stock-Based Compensation
Payout threshold range									33.00%
Maximum | 2012 Omnibus Incentive Plan | Performance shares
Stock-Based Compensation
Payout threshold range									170.00%
Maximum | 2018 Omnibus Incentive Plan | Performance shares
Stock-Based Compensation
Payout threshold range									170.00%
Series A-1 Preferred Stock
Preferred Stock
Preferred stock, shares authorized (in shares)							5,000,000		5,000,000
Preferred stock, shares issued (in shares)							0		0		0
Preferred stock, shares outstanding (in shares)							0		0		0