Stock Compensation Plans - Option Groups Outstanding (Details) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award
Options outstanding (in shares)	4,998,021	5,580,452
Options exercisable (in shares)	4,709,647
Options remaining contractual term	3 years 8 months 12 days
Weighted average exercise price for options outstanding (in dollars per share)	$ 20.61	$ 20.14
Weighted average exercise price for options exercisable (in dollars per share)	$ 19.83
Remaining weighted average contractual term for options exercisable	3 years 6 months
Grant Date February 27 2017
Share-based Compensation Arrangement by Share-based Payment Award
Options outstanding (in shares)	564,976
Options exercisable (in shares)	378,284
Options exercise price (in dollars per share)	$ 35.26
Options remaining contractual term	7 years 2 months 12 days
Grant Date February 22 2016
Share-based Compensation Arrangement by Share-based Payment Award
Options outstanding (in shares)	549,546
Options exercisable (in shares)	459,160
Options exercise price (in dollars per share)	$ 29.90
Options remaining contractual term	6 years 2 months 12 days
Grant Date February 23 2015
Share-based Compensation Arrangement by Share-based Payment Award
Options outstanding (in shares)	493,730
Options exercisable (in shares)	493,730
Options exercise price (in dollars per share)	$ 27.16
Options remaining contractual term	5 years 2 months 12 days
Grant Date February 24 2014
Share-based Compensation Arrangement by Share-based Payment Award
Options outstanding (in shares)	381,617
Options exercisable (in shares)	381,617
Options exercise price (in dollars per share)	$ 26.44
Options remaining contractual term	4 years 2 months 12 days
Grant Date February 28 2013
Share-based Compensation Arrangement by Share-based Payment Award
Options outstanding (in shares)	913,705
Options exercisable (in shares)	913,705
Options exercise price (in dollars per share)	$ 12.98
Options remaining contractual term	3 years 2 months 12 days
Grant Date February 27 2012
Share-based Compensation Arrangement by Share-based Payment Award
Options outstanding (in shares)	729,530
Options exercisable (in shares)	729,530
Options exercise price (in dollars per share)	$ 12.94
Options remaining contractual term	2 years 2 months 12 days
Grant Date February 22 2011
Share-based Compensation Arrangement by Share-based Payment Award
Options outstanding (in shares)	530,288
Options exercisable (in shares)	530,288
Options exercise price (in dollars per share)	$ 13.91
Options remaining contractual term	1 year 1 month 6 days
Grant Date February 23 2010
Share-based Compensation Arrangement by Share-based Payment Award
Options outstanding (in shares)	322,387
Options exercisable (in shares)	322,387
Options exercise price (in dollars per share)	$ 12.74
Options remaining contractual term	3 days
All Other Grant Dates
Share-based Compensation Arrangement by Share-based Payment Award
Options outstanding (in shares)	512,242
Options exercisable (in shares)	500,946
Options remaining contractual term	3 years 8 months 12 days
Other options exercise price range, lower range limit (in dollars per share)	$ 9.54
Other options exercise price range, upper range limit (in dollars per share)	32.72
Weighted average exercise price for options outstanding (in dollars per share)	20.27
Weighted average exercise price for options exercisable (in dollars per share)	$ 20.00
Remaining weighted average contractual term for options exercisable	3 years 7 months 6 days