Capital Stock and Share Based Compensation Plans - Cash proceeds (Details) - Stock Options - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cash received upon exercise		$ 4,641	$ 7,249	$ 16,579
Intrinsic value (market value on date of exercise less exercise price)		4,888	10,801	16,036
Tax benefits realized	[1]	$ 1,877	$ 4,101	$ 6,013

[1] (1) Benefits for 2015 were not recognized under prior accounting guidance until realized. In 2016, upon adoption of new accounting guidance, they are realized when generated.