Capital Stock - Common Shares in Treasury and Common Shares Outstanding (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Reconciliation Of Common Stock And Treasury Stock Balances [Roll Forward]
Beginning balance outstanding (in shares)	268,700,000	276,400,000
Shares sold (in shares)		825,000
Ending balance outstanding (in shares)	261,100,000	268,700,000	276,400,000
Proceeds from treasury stock issued	$ 11.7	$ 182.4
Shares in Treasury
Reconciliation Of Common Stock And Treasury Stock Balances [Roll Forward]
Beginning balance in treasury (in shares)	1,138,692	81,866,907	75,765,108
Shares tendered as payment for option rights exercised (in shares)	4,324	10,140	11,514
Shares tendered in connection with vesting of restricted stock units (in shares)	95,618	133,077	165,285
Treasury stock purchased (in shares)	(10,075,000)	(11,700,000)	(5,025,000)
Shares transferred from defined benefit pension plan (in shares)			(900,000)
Treasury stock, retired (in shares)		(91,746,432)
Shares sold (in shares)		825,000
Ending balance in treasury (in shares)	11,313,634	1,138,692	81,866,907
Shares Outstanding
Reconciliation Of Common Stock And Treasury Stock Balances [Roll Forward]
Beginning balance outstanding (in shares)	268,676,631	276,434,517	279,350,286
Shares issued for exercise of option rights (in shares)	2,365,168	2,873,646	2,705,634
Shares tendered as payment for option rights exercised (in shares)	(4,324)	(10,140)	(11,514)
Shares issued for vesting of restricted stock units (in shares)	276,948	386,685	480,396
Shares tendered in connection with vesting of restricted stock units (in shares)	(95,618)	(133,077)	(165,285)
Treasury stock purchased (in shares)	(10,075,000)	(11,700,000)	(5,025,000)
Shares transferred from defined benefit pension plan (in shares)			(900,000)
Shares sold (in shares)		825,000
Ending balance outstanding (in shares)	261,143,805	268,676,631	276,434,517