Commitments and Contingencies (Details) - lawsuit		1 Months Ended	30 Months Ended
	Mar. 30, 2017	Jan. 31, 2016	Jun. 30, 2018
Punitive Lawsuits Filed in the United States District Court for the Southern District of Texas
Loss Contingencies [Line Items]
Number of lawsuits dismissed (lawsuit)	4
Number of lawsuits filed (lawsuit)		1
Derivative Lawsuit Against Officers and Directors
Loss Contingencies [Line Items]
Number of lawsuits filed (lawsuit)		3
Derivative Lawsuit Filed in District Court of Harris County, Texas
Loss Contingencies [Line Items]
Number of lawsuits filed (lawsuit)		2	1