Share Incentive and Other Compensation - Employee 401 (k) Plan (Details)	6 Months Ended
	Jun. 30, 2018 USD ($)
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Employer matching contribution	50.00%
Maximum annual contribution per employee	6.00%
Maximum employee annual salary contribution	15.00%
Maximum employee annual salary contribution amount	$ 18,500