Capital Stock and Share Based Compensation Plans - Additional restricted stock and restricted stock unit vesting (Details) - Restricted Stock Units (RSUs) [Member] - 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]
Fair value of shares and units vested		$ 15,697	$ 12,906	$ 16,565
Tax benefits realized on shares and units vested	[1]	$ 5,965	$ 4,840	$ 6,212

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