Earnings per Share (Reconciliation of Number of Shares Used in Calculating Basic and Diluted Earnings per Share) (Details) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Earnings per Share [Line Items]
Basic weighted-average shares outstanding	67,315	67,149	67,275	67,263
Diluted weighted-average shares outstanding	67,648	67,528	67,588	67,535
Performance shares [Member]
Earnings per Share [Line Items]
Incremental shares	272	320	257	238
Restricted stock units [Member]
Earnings per Share [Line Items]
Incremental shares	61	59	56	34