Stockholders' Equity - Stock Based Compensation Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Increase (decrease) in share-based compensation expense	$ 2.8	$ (1.0)
Decrease in stock based compensation expense		$ 2.0
Percent of awards issued not expected to vest		50.00%
Percent of awards issued expected to vest		50.00%