SHARE INCENTIVE PLANS: (Details 4) (USD $)		12 Months Ended
	Feb. 28, 2007	Dec. 31, 2012 Employee Share Options	Dec. 31, 2011 Employee Share Options	Dec. 31, 2010 Employee Share Options	Dec. 31, 2012 Employee Share Purchase Plan	Dec. 31, 2011 Employee Share Purchase Plan	Dec. 31, 2010 Employee Share Purchase Plan
Share option plans
Maximum employee gross compensation percentage for ESPP participation					15.00%
ESPP purchase price percentage of market price					85.00%
Shares reserved for issuance pursuant to purchase rights under the ESPP	3,428,571
Maximum shares that can be issued and transferred					2,585,712
Maximum value of ordinary shares issued per employee pursuant to purchase rights under the ESPP per calendar year					$ 25,000
Shares issued under share-based compensation plan (in shares)					219,442	243,256
Weighted average price of shares issued (in dollars per share)					$ 28.57	$ 18.31
Stock authorized for future issuance					42,474
Weighted average assumptions are used to value share options
Expected volatility (as a percent)		56.60%	55.90%	59.80%	68.05%	41.80%	54.70%
Risk-free interest rate (as a percent)		1.02%	1.72%	2.18%	0.12%	0.10%	0.10%
Expected life		6 years 3 months	6 years 3 months	6 years 2 months 23 days	6 months 11 days	6 months 11 days	6 months 11 days