STOCK-BASED COMPENSATION (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant date fair value of shares issued (in dollars per share)	$ 48.96		$ 48.79
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Unvested at beginning of period (in shares)	257,259		235,929
Granted (in shares)	19,525		111,732
Forfeited (in shares)	0		0
Vested (in shares)	0		(70,877)
Unvested at end of period (in shares)	276,784		276,784
Weighted Average Grant Date Fair Value [Abstract]
Unvested at beginning of period (per share)	$ 41.77		$ 38.90
Granted (per share)	$ 48.96		$ 48.79
Forfeited (per share)	$ 0		$ 0
Vested (per share)	$ 0.00		$ 41.27
Unvested at end of period (per share)	$ 42.28		$ 42.28
Management Incentive Plan 2004 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Authorized shares of common stock	1,900,000		1,900,000
Shares available for grant	1,312,351		1,312,351
Stock-based compensation cost	$ 848,000	$ 554,000	$ 2,340,000	$ 1,348,000
Stock-based compensation costs capitalized as development costs	224,000	47,000	457,000	86,000
Management Incentive Plan 2004 [Member] | Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares withheld for tax obligations			17,927
Fair value of shares vested			3,191,000
Management Incentive Plan 2004 [Member] | Restricted Stock [Member] | Non-executive officers [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Granted (in shares)	19,525
Weighted Average Grant Date Fair Value [Abstract]
Share Based Compensation Arrangement By Share Based Payment Award Possible Shares To Be Awarded Vesting Rights	20.00%
Management Incentive Plan 2004 [Member] | Restricted Stock [Member] | Company Performance Awards [Member] | Executive Officer [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other Than Options, Potential Grants in Future Period (minimum)	0
Weighted Average Grant Date Fair Value [Abstract]
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other Than Options, Potential Grants in Future Period (maximum)	51,369
Share Based Compensation Arrangement by Share Based Payment Award, Equity Instruments Other Than Options, Percent of future vesting that will occur on grant date	20.00%
Share Based Compensation Arrangement By Share Based Payment Award Possible Shares To Be Awarded Vesting Rights	20.00%
Management Incentive Plan 2004 [Member] | Restricted Stock [Member] | Shareholder Return Awards [Member] | Executive Officer [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other Than Options, Potential Grants in Future Period (minimum)	0
Weighted Average Grant Date Fair Value [Abstract]
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other Than Options, Potential Grants in Future Period (maximum)	54,335
Share Based Compensation Arrangement by Share Based Payment Award, Equity Instruments Other Than Options, Percent of future vesting that will occur on grant date	25.00%
Share Based Compensation Arrangement By Share Based Payment Award Possible Shares To Be Awarded Vesting Rights	25.00%
Directors Equity Plan 2005 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Authorized shares of common stock	50,000		50,000
Stock-based compensation cost	$ 75,000	$ 60,000	$ 150,000	$ 120,000