Common Shares (Narrative) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands				6 Months Ended	9 Months Ended
	May 13, 2022	Apr. 12, 2022	Aug. 02, 2021	Jun. 30, 2022	Sep. 30, 2021	Sep. 30, 2020	Oct. 28, 2022	Oct. 26, 2022	Sep. 30, 2022	Dec. 31, 2021	Aug. 24, 2021
Number of common and preferred stock authorized to issue									185,000
Common shares, authorized									175,000	175,000
Preferred shares, authorized									10,000
Common Stock, Shares, Outstanding									106,500
Preferred Stock, Shares Outstanding									0
2021 ATM program
Maximum aggregate offering price of remaining common shares available for sale	$ 71,300
Maximum aggregate offering price of common shares			$ 500,000
Stock Issued During Period, Value, New Issues				$ 26,200
Stock Issued During Period, Shares, New Issues				200
AveragePricePerCommonShareSold				$ 165.01
2022 Equity offering
Stock Issued During Period, Value, New Issues		$ 490,300
Stock Issued During Period, Shares, New Issues		2,900
2022 ATM program
Maximum aggregate offering price of common shares	$ 500,000
2022 ATM program | Subsequent Event [Member]
Maximum aggregate offering price of remaining common shares available for sale							$ 500,000
2020 ATM program
Maximum aggregate offering price of remaining common shares available for sale											$ 200
Maximum aggregate offering price of common shares						$ 362,700
Stock Issued During Period, Value, New Issues					$ 358,800
Stock Issued During Period, Shares, New Issues					2,900
AveragePricePerCommonShareSold					$ 126.64
April 2007 Repurchase Plan [Member]
Treasury stock allowed for repurchase									$ 500,000
Share Repurchase Program, Remaining Authorized Repurchase Amount									$ 269,500
October 2022 Repurchase Plan | Subsequent Event [Member]
Treasury stock allowed for repurchase								$ 500,000
Share Repurchase Program, Remaining Authorized Repurchase Amount							$ 500,000