Share Capital - Changes in Number of Shares of Class A Stock Outstanding (Details) - Class A Stock - shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Class A Stock outstanding, beginning of year	13,530,688	13,377,967
Issued pursuant to shared-based compensation plans	131,524	152,721
Repurchased and canceled pursuant to the stock buy-back	(423,726)	0
Class A Stock outstanding, end of year	13,238,486	13,530,688