Capital Stock and Share Based Compensation Plans - Additional restricted stock and restricted stock unit vesting (Details) - Restricted Stock Units (RSUs) - 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]
Fair value of shares and units vested		$ 7,898	$ 15,697	$ 12,906
Tax benefits realized on shares and units vested	[1]	$ 3,033	$ 5,965	$ 4,840

[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.