Capital Stock and Share Based Compensation Plans - Cash proceeds (Details) - Stock Options - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cash received upon exercise		$ 7,249	$ 16,579	$ 46,624
Intrinsic value (market value on date of exercise less exercise price)		10,801	16,036	18,468
Tax benefits realized	[1]	$ 4,101	$ 6,013	$ 6,926

[1] Benefits for 2015 and 2013 to be recognized in future years when realizable.