Stock-Based Compensation (Details) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
	Dec. 20, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017	Jul. 12, 2017	Dec. 31, 2016	Dec. 31, 2015
Stock-Based Compensation
Share-based compensation expense		$ 6,743	$ 7,086	$ 8,122
Common stock, shares authorized					1,600,000,000		1,600,000,000
Common stock, shares issued					150,578,451		64,024,557
2018 Plan
Stock-Based Compensation
Restricted stock units outstanding					24,535		25,727
Unvested RSUs		8,887	7,301	7,301	5,400		8,887	7,301
Maximum percentage of fair market value per share granted	100.00%
Expiration of stock options	10 years
Common stock, shares authorized	8,323,764
Common stock, shares issued	0
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Balance at the beginning of the year		8,887	7,301
Shares granted (in shares)			6,375
Shares forfeited (in shares)		(1,192)	(250)
Shares vested (in shares)		(2,295)	(4,539)
Balance at the end of the year		5,400	8,887	7,301
Weighted Remaining Contractual Life (Years)		1 year 3 months 29 days	2 years 4 days	2 years 1 month 17 days
Aggregate Intrinsic Value					$ 1,633		$ 1,567	$ 1,587
Unrecognized compensation expense					$ 6,000
Unrecognized compensation expense, recognition period		1 year 3 months 29 days
Restricted stock units (RSUs) | 2013 Long Term Incentive Plan
Stock-Based Compensation
Restricted stock units outstanding					24,535
Unvested RSUs						9,880
Share-based compensation expense		$ 6,700	$ 7,100
Restricted stock units (RSUs) | 2013 Long Term Incentive Plan | Minimum
Stock-Based Compensation
Vesting period of remaining RSU's which will vest by 2019		3 years
Restricted stock units (RSUs) | 2013 Long Term Incentive Plan | Maximum
Stock-Based Compensation
Vesting period of remaining RSU's which will vest by 2019		4 years
Non-employee advisors
Awards to Non-employees
Compensation expense		$ 28,600
Fair value per share		$ 8.00
Common Stock | Non-employee advisors
Awards to Non-employees
Stock issued		3,609,375