SHARE INCENTIVE PLANS: (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended		1 Months Ended			12 Months Ended				1 Months Ended		12 Months Ended
	Dec. 31, 2012 item	Feb. 28, 2007	Jan. 31, 2013 Global Plan	Jan. 31, 2012 Global Plan	Jan. 31, 2011 Global Plan	Dec. 31, 2012 Global Plan	Dec. 31, 2012 Share options	Dec. 31, 2011 Share options	Dec. 31, 2010 Share options	Jan. 31, 2013 Assumption Plan	Jan. 31, 2012 Assumption Plan	Dec. 31, 2011 Assumption Plan
SHARE INCENTIVE PLANS:
Number of share option plans	5
Share option plans
Number of shares authorized for issuance		3,428,571					1,085,712
Maximum annual percentage increase in ordinary shares reserved for issuance						2.00%
Maximum annual increase in ordinary shares reserved for issuance						685,714						281,625
Maximum shares that can be issued and transferred						15,474,018
Total shares reserved for future issuance (in shares)	7,461,817
Increase in shares reserved for issuance			685,714	685,714	685,714					281,625	281,625
Stock option activity under equity incentive plans
Options outstanding at the beginning of the period (in shares)							4,706,349	5,434,974	6,403,679
Options granted (in shares)							879,160	1,060,938	605,340
Options exercised (in shares)							(2,161,628)	(1,586,577)	(1,338,223)
Options cancelled (in shares)							(137,959)	(202,986)	(235,822)
Options outstanding at the end of the period (in shares)							3,285,922	4,706,349	5,434,974
Weighted average exercise price of options outstanding
Options outstanding at the beginning of the period (in dollars per share)							$ 13.42	$ 10.56	$ 8.38
Options granted (in dollars per share)							$ 70.72	$ 21.80	$ 21.73
Options exercised (in dollars per share)							$ 10.96	$ 8.83	$ 5.15
Options cancelled (in dollars per share)							$ 28.33	$ 16.46	$ 10.99
Options outstanding at the end of the period (in dollars per share)							$ 29.74	$ 13.42	$ 10.56
Weighted average fair value of options granted (in dollars per share)							$ 38.66	$ 18.51	$ 12.51
Total pretax intrinsic value of options exercised							$ 136.1
Closing price of ordinary shares (in dollars per share)							$ 59.38
Total pretax intrinsic value of all outstanding options							112.4
Total pretax intrinsic value of all exercisable options							$ 88.4