Share Capital - Changes in Number of Shares of Class A Stock Outstanding (Details) - Class A Stock [Member] - shares	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Class of Stock [Line Items]
Class A Stock outstanding, beginning of period (in shares)	13,263,532	13,634,831	13,238,486	13,530,688	13,530,688
Issued pursuant to shared-based compensation plans (in shares)	7,163	15,318	272,483	119,461
Repurchased and canceled pursuant to the stock buy-back (in shares)	(10,980)	0	(251,254)	0
Class A Stock outstanding, end of period (in shares)	13,259,715	13,650,149	13,259,715	13,650,149	13,238,486