STOCK PLANS (Details) (USD $) In Thousands, except Share data, unless otherwise specified		12 Months Ended
	Dec. 31, 2011	Dec. 31, 2011 Stock options Y	Dec. 31, 2010 Stock options Y	Dec. 31, 2009 Stock options Y	Apr. 28, 2006 EPI Plan	Apr. 28, 2006 Director Plan
Stock Plans
Maximum additional number of the Company's common shares that may be granted					6,000,000	600,000
Common shares available for future grant under all plans	3,061,346
Stock Options, Shares
Balance at beginning of year (in shares)		3,779,824	3,596,884	3,110,978
Shares granted (in shares)		459,263	491,010	583,660
Shares exercised (in shares)		(572,795)	(260,084)	(59,102)
Shares canceled (in shares)		(33,829)	(47,986)	(38,652)
Balance at end of year (in shares)		3,632,463	3,779,824	3,596,884
Exercisable at end of year (in shares)		2,677,071	2,749,168	2,668,692
Stock Options, Weighted Average Exercise Price
Balance at beginning of year (in dollars per share)		$ 23.99	$ 22.28	$ 21.37
Shares granted (in dollars per share)		$ 35.34	$ 31.29	$ 26.31
Shares exercised (in dollars per share)		$ 19.82	$ 13.49	$ 11.92
Shares canceled (in dollars per share)		$ 26.62	$ 27.84	$ 25.75
Balance at end of year (in dollars per share)		$ 26.05	$ 23.99	$ 22.28
Exercisable at end of year (in dollars per share)		$ 23.73	$ 22.40	$ 20.91
Weighted average assumptions used for estimating fair value of options granted
Expected volatility (as a percent)		41.92%	42.15%	40.48%
Dividend yield (as a percent)		1.63%	2.02%	2.15%
Risk-free interest rate (as a percent)		0.80%	1.64%	2.04%
Expected option life (in years)		4.3	4.9	4.7
Weighted average fair value per option granted during the year (in dollars per share)		$ 10.97	$ 10.01	$ 8.03
Nonvested stock options, Number of Options
Balance at beginning of year (in shares)		980,926
Granted (in shares)		459,263	491,010	583,660
Vested (in shares)		(483,245)
Forfeited (in shares)		(27,562)
Balance at end of year (in shares)		929,382	980,926
Nonvested stock options, Weighted Average Fair Value at Grant Date
Balance at beginning of year (in dollars per share)		$ 8.74
Granted (in dollars per share)		$ 12.02
Vested (in dollars per share)		$ 7.95
Forfeited (in dollars per share)		$ 8.39
Balance at end of year (in dollars per share)		$ 10.78	$ 8.74
Stock Options, additional disclosures
Award expiration (in years)		10 years
Award vesting period (in years)		3 years
Aggregate intrinsic value of awards outstanding		$ 47,467
Aggregate intrinsic value of awards exercisable		41,192
Total intrinsic value of awards exercised		$ 15,781	$ 5,006