Stockholders' Equity - Series A Preferred Stock and Stock Repurchases (Details) $ / shares in Units, $ in Millions	1 Months Ended		12 Months Ended
	May 31, 2014 shares	Nov. 30, 2013 USD ($) $ / shares shares	Dec. 31, 2014 shares	Dec. 31, 2016 shares	Dec. 31, 2015 shares	Dec. 31, 2012 shares
Convertible Preferred Stock and Stockholders' Equity
Common stock, shares authorized		150,000,000		1,000,000,000	1,000,000,000	147,000,000
Common Stock
Convertible Preferred Stock and Stockholders' Equity
Shares sold			8,941,250
Shares of common stock issued for conversion of Series A	2,857,143
Vulcan
Convertible Preferred Stock and Stockholders' Equity
Aggregate purchase price for preferred stock and warrants | $		$ 30.0
Vulcan | Common Stock Purchase Warrants
Convertible Preferred Stock and Stockholders' Equity
Number of shares that may be purchased under warrant		666,666
Exercise price of warrants (in dollars per share) | $ / shares		$ 15.00
Series A
Convertible Preferred Stock and Stockholders' Equity
Preferred stock, shares authorized		4,500,000
Series A | Vulcan
Convertible Preferred Stock and Stockholders' Equity
Shares sold		2,857,143
Private placement price per share (in dollars per share) | $ / shares		$ 10.50
Conversion ratio	1