Earnings Per Share and Shareholders' Equity Transactions (Narrative) (Details) - USD ($)						12 Months Ended			36 Months Ended
	Jan. 29, 2021	Oct. 29, 2020	Feb. 26, 2020	Dec. 09, 2019	Jun. 28, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2020
Accelerated Share Repurchase Agreement [Member]
Class Of Stock [Line Items]
Stock repurchase program, available authorized repurchase amount						$ 124,000,000			$ 124,000,000
Repurchased common shares									5,200,000
Accelerated Share Repurchase Agreement [Member] | Maximum [Member]
Class Of Stock [Line Items]
Repurchases common stock, authorized						$ 900,000,000			$ 900,000,000
December 30, 2018 and June 28, 2019 Accelerated Share Repurchase Agreement [Member]
Class Of Stock [Line Items]
Repurchased common shares					3,200,000
Repurchased common shares, amount					$ 400,000,000.0
December 2019 Accelerated Share Repurchase Agreement [Member]
Class Of Stock [Line Items]
Repurchased common shares				900,000
Repurchased common shares, amount				$ 150,000,000.0
Common stock shares received as final settlement of shares repurchased			200,000
Shares repurchased under repurchase agreement, percentage				80.00%
October 2020 ASR [Member]
Class Of Stock [Line Items]
Amount paid by company		$ 100,000,000.0
Initial delivery of shares of common stock received		800,000
Shares repurchased under repurchase agreement, percentage		80.00%
October 2020 ASR [Member] | Subsequent Event [Member]
Class Of Stock [Line Items]
Common stock shares received as final settlement of shares repurchased	45,000
Stock Compensation Plans [Member]
Class Of Stock [Line Items]
Antidilutive securities excluded from calculation of earnings per share						400,000	200,000	300,000