Stock-Based Compensation Plans (Summary of Stock Option Activity) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Employee Stock Option Plan
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Shares, Outstanding at Beginning of Year (in shares)	17,692	17,829	18,000
Shares, Granted (in shares)	3,227	2,966	5,757
Shares, Exercised (in shares)	(6,291)	(2,344)	(5,224)
Shares, Forfeited (in shares)	(376)	(759)	(704)
Shares, Outstanding at End of Year (in shares)	14,252	17,692	17,829
Shares, Exercisable at End of Year (in shares)	4,855	6,858	4,564
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Wtd. Avg. Ex. Price, Outstanding at Beginning of Year (in dollars per share)	$ 14	$ 13	$ 12
Wtd. Avg. Ex. Price, Granted (in dollars per share)	17	17	15
Wtd. Avg. Ex. Price, Exercised (in dollars per share)	12	12	11
Wtd. Avg. Ex. Price, Forfeited (in dollars per share)	15	14	13
Wtd. Avg. Ex. Price, Outstanding at End of Year (in dollars per share)	15	14	13
Wtd. Avg. Ex. Price, Exercisable at End of Year (in dollars per share)	$ 14	$ 13	$ 12
Option expiration period, years	3 years	3 years	3 years 6 months
Wtd. Avg. Remaining Contract Life, Exercisable at End of Year	2 years 3 months 18 days	2 years 1 month 6 days	2 years 3 months 18 days
Aggregate Intrinsic Value, Exercised	$ 31,790	$ 11,596	$ 26,618
Aggregate Intrinsic Value, Outstanding at End of Year	67,763	45,842	90,759
Aggregate Intrinsic Value, Exercisable at End of Year	$ 30,021	$ 23,917	$ 28,342
Non-Employee Director Stock Option Plan
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Shares, Outstanding at Beginning of Year (in shares)	373	381	462
Shares, Granted (in shares)	56	49	98
Shares, Exercised (in shares)	(36)	(57)	(167)
Shares, Forfeited (in shares)	(12)	0	(12)
Shares, Outstanding at End of Year (in shares)	381	373	381
Shares, Exercisable at End of Year (in shares)	381	373	381
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Wtd. Avg. Ex. Price, Outstanding at Beginning of Year (in dollars per share)	$ 13	$ 12	$ 11
Wtd. Avg. Ex. Price, Granted (in dollars per share)	16	17	14
Wtd. Avg. Ex. Price, Exercised (in dollars per share)	10	11	10
Wtd. Avg. Ex. Price, Forfeited (in dollars per share)	16	0	16
Wtd. Avg. Ex. Price, Outstanding at End of Year (in dollars per share)	14	13	12
Wtd. Avg. Ex. Price, Exercisable at End of Year (in dollars per share)	$ 14	$ 13	$ 12
Option expiration period, years	6 years 4 months 24 days	6 years 4 months 24 days	6 years 8 months 12 days
Wtd. Avg. Remaining Contract Life, Exercisable at End of Year	6 years 4 months 24 days	6 years 4 months 24 days	6 years 8 months 12 days
Aggregate Intrinsic Value, Exercised			$ 893
Aggregate Intrinsic Value, Outstanding at End of Year	2,180	1,069	2,137
Aggregate Intrinsic Value, Exercisable at End of Year	$ 2,180	$ 1,069	$ 2,137