Share Capital - Changes in Number of Shares of Class A Stock Outstanding (Details) - Class A Stock [Member] - shares	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Class of Stock [Line Items]
Class A Stock outstanding, beginning of period (in shares)	13,259,715	13,650,149	13,238,486	13,530,688	13,530,688
Issued pursuant to shared-based compensation plans (in shares)	10,988	12,063	283,471	131,524
Repurchased and canceled pursuant to the stock buy-back (in shares)	(2,264)	(328,844)	(253,518)	(328,844)
Class A Stock outstanding, end of period (in shares)	13,268,439	13,333,368	13,268,439	13,333,368	13,238,486