Earnings Per Share (Details) - shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Weighted-average shares:
Common shares outstanding	77,447,263	78,219,458	78,161,494
Restricted common shares	476,726	556,592	653,944
Total weighted average shares	77,923,989	78,776,050	78,815,438
Percentage of weighted-average shares:
Common shares outstanding	99.39%	99.29%	99.17%
Restricted common shares	0.61%	0.71%	0.83%
Total	100.00%	100.00%	100.00%