Stockholders' Equity - Summary of Warrant Activity (Details) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Weighted Average Exercise Price, Beginning balance ($ per share)	$ 6.78	$ 6.78	$ 6.39
Weighted Average Exercise Price, Granted ($ per share)	0.00	0.00	0.00
Weighted Average Exercise Price, Ending balance ($ per share)	6.78	$ 6.78	$ 6.78
Weighted Average Exercise Price, Exercisable ($ per share)	$ 6.78
Exercise of Issued Warrants [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Number of shares, outstanding beginning	445,000	445,000	445,000
Number of shares, granted	0	0	0
Number of shares, outstanding ending balance	445,000	445,000	445,000
Number of shares, exerciseable	445,000