Stockholders' Equity - Stock Options (Details) - shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Class of Stock
Common stock, shares reserved for future issuance	76,137,792
Maximum number of additional common shares	6,946,975
Minimum option exercise price as a percentage of market value of common stock	100.00%
Common stock options outstanding	18,002,000	16,261,000
Options outstanding under earlier plans	4,616,437
Grant of inducement stock option	1,150,000
Inducement grants outstanding shares	3,150,000
2013 Stock Incentive Plan
Class of Stock
Stock options, expiration period	10 years
Common stock, shares reserved for future issuance	15,224,460
Maximum number of shares that may be granted to any one individual in single year	1,500,000
Common stock options outstanding	10,235,083
Common shares available for grant	6,275,852
Minimum | 2013 Stock Incentive Plan
Class of Stock
Stock options, vesting period	3 years
Maximum | 2013 Stock Incentive Plan
Class of Stock
Stock options, vesting period	4 years