Earnings Per Share and Shareholders' Equity Transactions (Narrative) (Details) - USD ($)			12 Months Ended
	Dec. 09, 2019	Dec. 05, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Class Of Stock [Line Items]
Antidilutive securities excluded from calculation of earnings per share			200,000	300,000	400,000
Accelerated Share Repurchase Agreement [Member]
Class Of Stock [Line Items]
Increase in repurchases common stock, authorized		$ 300,000,000
Accelerated Share Repurchase Agreement [Member] | Maximum [Member]
Class Of Stock [Line Items]
Repurchases common stock, authorized			$ 900,000,000
December 2018 and June 2019 Accelerated Share Repurchase Agreement [Member]
Class Of Stock [Line Items]
Repurchased common shares, amount			$ 400,000,000.0
Repurchased common shares			3,200,000
December 2019 Accelerated Share Repurchase Agreement [Member]
Class Of Stock [Line Items]
Amount paid by company	$ 150,000,000.0
Initial delivery of shares of common stock received	900,000
Shares repurchased under repurchase agreement, percentage	80.00%