Stockholders' Equity - Preferred Stock (Details)	9 Months Ended
	Sep. 30, 2018 $ / shares shares	Dec. 31, 2017 shares
Class of Stock [Line Items]
Number of preferred shares authorized in amendment (in shares)	5,000,000
Series A Preferred Stock
Class of Stock [Line Items]
Number of preferred shares authorized in amendment (in shares)	2,000,000
Preferred stock issued (in shares)	2,000,000	2,000,000
Preferred stock outstanding (in shares)	2,000,000	2,000,000
Dividend price (in dollars per share) | $ / shares	$ 22.85
Series A Preferred Stock | Founders Entities
Class of Stock [Line Items]
Convertible preferred stock conversion ratio	1
Extension period for conversion	3 years