XML 53 R58.htm IDEA: XBRL DOCUMENT v2.4.0.8
Share Capital - Changes in Number of Shares of Class A Stock Outstanding (Detail) (Class A Stock [Member])
 3 Months Ended 9 Months Ended
Sep. 30, 2013
Sep. 30, 2012
Sep. 30, 2013
Sep. 30, 2012
Oct. 07, 2011
Class A Stock [Member]
          
Class of Stock [Line Items]          
Class A Stock outstanding, beginning of period 13,496,783 13,489,162 13,508,318 13,572,265 13,572,265
Issued pursuant to shared-based compensation plans 65,227 40,850 65,227 57,647  
Repurchased and cancelled pursuant to the stock buy-back (119,251) (15,000) (130,786) (114,900)  
Class A Stock outstanding, end of period 13,442,759 13,515,012 13,442,759 13,515,012 13,572,265