Earnings per Share Earnings per Share (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Weighted average common shares—basic	45,721,155	45,435,936	45,669,782	45,381,592
Weighted average common shares—diluted	46,029,361	45,760,455	45,953,578	45,713,873
Restricted Shares [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Incremental common shares attributable to share-based payment arrangements	233,859	244,757	226,617	248,942
Stock Options [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Incremental common shares attributable to share-based payment arrangements	74,347	79,762	57,179	83,339