Share-Based Compensation - Performance-Based Awards Granted (Details) - Performance Based Awards - shares	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Performance Period Ending December 2020
Share-based Compensation
Number of shares granted	79,218
Performance Period Ending December 2018
Share-based Compensation
Number of shares granted	84,444
Performance period ending December 2019, Tranche one
Share-based Compensation
Number of shares granted		99,492
Performance Period Ending December 2019
Share-based Compensation
Number of shares granted	11,304
Performance Period Ending December 2017
Share-based Compensation
Number of shares granted		146,094