Subsequent Event (Details) - $ / shares	Nov. 06, 2018	Sep. 30, 2018	Dec. 31, 2017
Subsequent Events
Common stock, par value (in dollars per share)		$ 0.01	$ 0.01
Subsequent event
Subsequent Events
Common stock, par value (in dollars per share)	$ 0.01
Subsequent event | Merger Agreement
Subsequent Events
Merger consideration per share	$ 30.30