Share capital (Tables)

3 Months Ended

Mar. 31, 2013

Equity [Abstract]

Changes in Number of Shares of Class A Stock Outstanding

The following table reflects changes in the number of shares of Class A Stock outstanding for the periods indicated:

	Three months ended March 31,
	2013		2012
Class A Stock outstanding, beginning of period		13,508,318		13,572,265
Issued pursuant to shared-based compensation plans		—		16,797
Repuchsed and cancelled pursuant to the stock buy-back		—		(99,900	)
Class A Stock outstanding, end of period		13,508,318		13,489,162