Shareholders' Equity - Changes in Common Shares (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Common Stock Outstanding Rollforward [Roll Forward]
Beginning Balance (in shares)	53,792	53,637	53,457
Shares issued due to vesting of share-based compensation awards (in shares)	54	132	135
Other shares issued for compensation and shares reissued to stock purchase plan (in shares)	47	23	45
Ending Balance (in shares)	53,893	53,792	53,637