Stock-Based Compensation - Summary of Stock Option Awards Granted (Details)	9 Months Ended	12 Months Ended
	Sep. 30, 2015 employee	Dec. 31, 2017 employee $ / shares shares	Dec. 31, 2016 employee $ / shares shares	Dec. 31, 2015 $ / shares shares
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Number of Options Granted (shares) | shares		990,566
Weighted Average Exercise Price (usd per share)		$ 6.82
Director group
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Vesting Period		1 year		1 year
Weighted Average Grant Date Fair Value (usd per share)		$ 6.35		$ 4.02
Employee group
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Vesting Period		3 years	2 years	3 years
Weighted Average Grant Date Fair Value (usd per share)		$ 6.31	$ 4.88	$ 3.99
Director group (3)
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Number of Options Granted (shares) | shares			20,417
Employee inducement
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Vesting Period		3 years	3 years	3 years
Weighted Average Grant Date Fair Value (usd per share)		$ 6.33	$ 4.94	$ 5.29
Options | Director group
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Number of Options Granted (shares) | shares		90,566		249,273
Vesting Period		1 year		1 year
Weighted Average Exercise Price (usd per share)		$ 6.34		$ 4.49
Weighted Average Grant Date Fair Value (usd per share)		$ 3.49		$ 2.44
Options | Director group (1)
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Number of Options Granted (shares) | shares		35,000	35,000
Vesting Period		3 years	3 years
Weighted Average Exercise Price (usd per share)		$ 6.25	$ 4.80
Weighted Average Grant Date Fair Value (usd per share)		$ 3.50	$ 2.66
Number of employees granted non-qualified stock options | employee		1
Options | CEO grant
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Number of Options Granted (shares) | shares		500,000
Vesting Period		4 years
Weighted Average Exercise Price (usd per share)		$ 7.35
Weighted Average Grant Date Fair Value (usd per share)		$ 2.36
Options | Employee group
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Number of Options Granted (shares) | shares		30,000		17,092
Vesting Period		3 years		3 years
Weighted Average Exercise Price (usd per share)		$ 7.25		$ 3.99
Weighted Average Grant Date Fair Value (usd per share)		$ 3.99		$ 1.33
Options | Director group (3)
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Number of Options Granted (shares) | shares			195,417
Vesting Period			1 year
Weighted Average Exercise Price (usd per share)			$ 5.01
Weighted Average Grant Date Fair Value (usd per share)			$ 2.71
Number of employees granted non-qualified stock options | employee			1
Options | Employee inducement
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Number of Options Granted (shares) | shares		335,000	232,500	135,000
Vesting Period		3 years	3 years	3 years
Weighted Average Exercise Price (usd per share)		$ 6.19	$ 4.61	$ 5.51
Weighted Average Grant Date Fair Value (usd per share)		$ 3.41	$ 2.60	$ 1.42
Number of employees granted non-qualified stock options | employee	3