CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Other comprehensive income (loss), net of tax:
Dividends: declared and paid (in dollars per share)	$ 0.92	$ 0.80	$ 0.60
Repurchase of class A common shares (in shares)	3,986,275	15,447,884	3,917,471
Convert Voting Shares to Class A Common Shares (in shares)	466,690
Exercise of employee share options: shares issued (in shares)	285,938	1,007,676	990,383
Other share-based compensation, net: shares issued (in shares)	515,010	513,690	352,599
Other share-based compensation, net: shares repurchased (in shares)	164,104	175,239	104,178