STOCK-BASED COMPENSATION (Details) (USD $)	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Management Incentive Plan 2004 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Authorized shares of common stock (in shares)	1,900,000
Shares available for grant (in shares)	1,331,876
Stock-based compensation cost	$ 1,492,000	$ 794,000
Stock-based compensation costs capitalized as development costs	233,000	39,000
Management Incentive Plan 2004 [Member] | Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share awards granted (in shares)	92,207
Grant date fair value of shares issued (in dollars per share)	$ 48.75
Shares withheld for tax obligations (in shares)	17,927
Fair value of shares vested	3,191,000
Restricted Stock Activity [Roll Forward]
Nonvested at Start of period (in shares)	235,929
Granted (in shares)	92,207
Forfeited (in shares)	0
Vested (in shares)	(70,877)
Nonvested at end of period (in shares)	257,259
Weighted Average Grant Date Fair Value [Abstract]
Nonvested at beginning of period (per share)	$ 38.90
Granted (per share)	$ 48.75
Forfeited (per share)	$ 0.00
Vested (per share)	$ 41.27
Nonvested at end of period (per share)	$ 41.77
Management Incentive Plan 2004 [Member] | Restricted Stock [Member] | Company Performance Awards [Member] | Executive Officers [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share awards granted (in shares)	44,789
Grant date fair value of shares issued (in dollars per share)	$ 48.75
Vesting Rights	shares vested 20% on the dates shares were determined and awarded and will vest 20% per year on January 1 of the subsequent four years
Restricted Stock Activity [Roll Forward]
Granted (in shares)	44,789
Weighted Average Grant Date Fair Value [Abstract]
Granted (per share)	$ 48.75
Management Incentive Plan 2004 [Member] | Restricted Stock [Member] | Shareholder Return Awards [Member] | Executive Officers [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share awards granted (in shares)	47,418
Grant date fair value of shares issued (in dollars per share)	$ 48.75
Vesting Rights	shares vested 25% on the dates shares were determined and awarded and will vest 25% per year on January 1 in years 2013, 2014 and 2015
Restricted Stock Activity [Roll Forward]
Granted (in shares)	47,418
Weighted Average Grant Date Fair Value [Abstract]
Granted (per share)	$ 48.75
Directors Equity Plan 2005 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Authorized shares of common stock (in shares)	50,000
Stock-based compensation cost	$ 75,000	$ 60,000