STOCK-BASED COMPENSATION PLAN (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Number of shares in the aggregate that may be issued under the 1997 Stock-Based Compensation Plan	2,000,000		2,000,000
Number of options granted			0	0
Fair value per share (in dollars per share)	$ 50.780		$ 50.780
Cost	$ 757,000	$ 752,000	$ 1,521,000	$ 1,402,000
Capitalized	(63,000)	(58,000)	(126,000)	(115,000)
Net expense	694,000	694,000	1,395,000	1,287,000
Unrecognized compensation cost of awards granted under the plan	4,000,000		4,000,000
Weighted average period over which unrecognized compensation cost is to be recognized (in years)			1 year 10 months 24 days
Additional disclosures [Abstract]
Weighted average fair value nonvested shares-beginning balance (in dollars per share)			$ 51.292
Weighted average fair value nonvested shares-granted during the period (in dollars per share)			$ 48.488
Weighted average fair value nonvested shares-cancelled/forfeited during the period (in dollars per share)			$ 50.302
Weighted average fair value nonvested shares-vested during the period (in dollars per share)			$ 45.809
Weighted average fair value nonvested shares-ending balance (in dollars per share)	$ 50.780		$ 50.780
Officers and Key Employees [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Number of shares granted			56,464	40,955
Vesting period of shares (in years)			3 years
The range of the actual amount of shares that ultimately vest of the original share units granted (in hundredths)			0% to 150%
Shares outstanding (in shares)	135,775		135,775
Cost	566,000	524,000	1,139,000	1,048,000
Restricted stock award activity, excluding accrued dividend equivalents [Roll Forward]
Nonvested shares outstanding, beginning balance (in shares)			81,005
Granted (in shares)			56,464	40,955
Cancelled/Forfeited (in shares)			(1,694)
Vested (in shares)			0
Nonvested shares outstanding, ending balance (in shares)	135,775		135,775
Additional disclosures [Abstract]
Number of shares awarded during the period			66,077	33,322
Market value of shares awarded			3,300,000	1,900,000
Officers and Key Employees [Member] | Grant Date January 2011 - TSR [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Shares outstanding (in shares)	40,069		40,069
Fair value per share (in dollars per share)	$ 50.940		$ 50.940
Expected volatility (in hundredths)			27.50%
Risk-free interest rate (in hundredths)			1.01%
Restricted stock award activity, excluding accrued dividend equivalents [Roll Forward]
Nonvested shares outstanding, ending balance (in shares)	40,069		40,069
Additional disclosures [Abstract]
Weighted average fair value nonvested shares-ending balance (in dollars per share)	$ 50.940		$ 50.940
Officers and Key Employees [Member] | Grant Date January 2012 - TSR [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Shares outstanding (in shares)	20,090		20,090
Fair value per share (in dollars per share)	$ 51.230		$ 51.230
Expected volatility (in hundredths)			22.50%
Risk-free interest rate (in hundredths)			0.43%
Restricted stock award activity, excluding accrued dividend equivalents [Roll Forward]
Nonvested shares outstanding, ending balance (in shares)	20,090		20,090
Additional disclosures [Abstract]
Weighted average fair value nonvested shares-ending balance (in dollars per share)	$ 51.230		$ 51.230
Officers and Key Employees [Member] | Grant Date January 2012 - EPS [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Shares outstanding (in shares)	20,090		20,090
Fair value per share (in dollars per share)	$ 56.930		$ 56.930
Restricted stock award activity, excluding accrued dividend equivalents [Roll Forward]
Nonvested shares outstanding, ending balance (in shares)	20,090		20,090
Additional disclosures [Abstract]
Weighted average fair value nonvested shares-ending balance (in dollars per share)	$ 56.930		$ 56.930
Officers and Key Employees [Member] | Grant Date January 2013 - TSR [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Shares outstanding (in shares)	27,763		27,763
Fair value per share (in dollars per share)	$ 44.380		$ 44.380
Expected volatility (in hundredths)			21.10%
Risk-free interest rate (in hundredths)			0.40%
Restricted stock award activity, excluding accrued dividend equivalents [Roll Forward]
Nonvested shares outstanding, ending balance (in shares)	27,763		27,763
Additional disclosures [Abstract]
Weighted average fair value nonvested shares-ending balance (in dollars per share)	$ 44.380		$ 44.380
Officers and Key Employees [Member] | Grant Date January 2013 - EPS [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Shares outstanding (in shares)	27,763		27,763
Fair value per share (in dollars per share)	$ 51.180		$ 51.180
Restricted stock award activity, excluding accrued dividend equivalents [Roll Forward]
Nonvested shares outstanding, ending balance (in shares)	27,763		27,763
Additional disclosures [Abstract]
Weighted average fair value nonvested shares-ending balance (in dollars per share)	$ 51.180		$ 51.180
Directors [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Number of shares granted			12,285	9,904
Vesting period of shares (in years)			3 years
Shares Vested, Directors (in hundredths)	100.00%		100.00%
Shares outstanding (in shares)	19,617		19,617
Cost	191,000	228,000	382,000	354,000
Restricted stock award activity, excluding accrued dividend equivalents [Roll Forward]
Nonvested shares outstanding, beginning balance (in shares)			27,688
Granted (in shares)			12,285	9,904
Cancelled/Forfeited (in shares)			0
Vested (in shares)			(20,356)
Nonvested shares outstanding, ending balance (in shares)	19,617		19,617
Additional disclosures [Abstract]
Market value of shares awarded			$ 600,000	$ 600,000
Directors [Member] | Grant Date January 2011 [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Shares outstanding (in shares)	7,332		7,332
Fair value per share (in dollars per share)	$ 52.940		$ 52.940
Expected volatility (in hundredths)			0.00%
Risk-free interest rate (in hundredths)			0.00%
Restricted stock award activity, excluding accrued dividend equivalents [Roll Forward]
Nonvested shares outstanding, ending balance (in shares)	7,332		7,332
Additional disclosures [Abstract]
Weighted average fair value nonvested shares-ending balance (in dollars per share)	$ 52.940		$ 52.940
Directors [Member] | Grant Date January 2013 [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Shares outstanding (in shares)	12,285		12,285
Fair value per share (in dollars per share)	$ 51.740		$ 51.740
Expected volatility (in hundredths)			0.00%
Risk-free interest rate (in hundredths)			0.00%
Restricted stock award activity, excluding accrued dividend equivalents [Roll Forward]
Nonvested shares outstanding, ending balance (in shares)	12,285		12,285
Additional disclosures [Abstract]
Weighted average fair value nonvested shares-ending balance (in dollars per share)	$ 51.740		$ 51.740
Minimum [Member] | Officers and Key Employees [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Percentage of actual amount of shares that ultimately vest of original share units granted			0.00%
Maximum [Member] | Officers and Key Employees [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Percentage of actual amount of shares that ultimately vest of original share units granted			150.00%
Stock Appreciation Rights (SARs) [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Number of shares granted			0	0
Restricted stock award activity, excluding accrued dividend equivalents [Roll Forward]
Granted (in shares)			0	0