Stock-Based Compensation Plans (Summary of Stock Option Activity) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Shares (000)
Shares, Outstanding at Beginning of Year (in shares)	8,944	11,837	14,252
Shares, Granted (in shares)	1,049	1,613	1,295
Shares, Exercised (in shares)	(4,402)	(4,278)	(3,476)
Shares, Forfeited (in shares)	(156)	(228)	(234)
Shares, Outstanding at End of Year (in shares)	5,435	8,944	11,837
Shares, Exercisable at End of Year (in shares)	1,859	4,101	5,297
Wtd. Avg Grant Date Fair Value
Wtd. Avg. Ex. Price, Outstanding at Beginning of Year (in dollars per share)	$ 18	$ 16	$ 15
Wtd. Avg. Ex. Price, Granted (in dollars per share)	25	22	20
Wtd. Avg. Ex. Price, Exercised (in dollars per share)	16	15	13
Wtd. Avg. Ex. Price, Forfeited (in dollars per share)	20	18	16
Wtd. Avg. Ex. Price, Outstanding at End of Year (in dollars per share)	20	18	16
Wtd. Avg. Ex. Price, Exercisable at End of Year (in dollars per share)	$ 18	$ 16	$ 15
Option expiration period, years	3 years 1 month 6 days	2 years 9 months 18 days	2 years 8 months 12 days
Wtd. Avg. Remaining Contract Life, Exercisable at End of Year	2 years 2 months 12 days	1 year 8 months 12 days	2 years
Aggregate Intrinsic Value, Exercised	$ 36,294	$ 38,097	$ 25,156
Aggregate Intrinsic Value, Outstanding at End of Year	47,170	24,881	58,202
Aggregate Intrinsic Value, Exercisable at End of Year	$ 20,484	$ 16,162	$ 32,152