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As of the balance sheet date, the aggregate unrecognized cost of equity-based awards made to employees under equity-based compensation awards that have yet to vest.

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Description of the period of time over which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, which may be expressed in a variety of ways (for example, in years, month and year).

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Equity-based compensation cost during the period with respect to the award, which will be recognized in income (as well as the total recognized tax benefit) or capitalized as part of the cost of an asset.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.

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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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The risk-free interest rate assumption that is used in valuing an option on its own shares.

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The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

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STOCK-BASED COMPENSATION PLAN (Details) (USD $)	3 Months Ended		9 Months Ended
STOCK-BASED COMPENSATION PLAN (Details) (USD $)	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
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
Fair value per share	$ 42.901		$ 42.901
Cost	$ 577,000	$ 504,000	$ 1,966,000	$ 1,540,000
Capitalized	(55,000)	(50,000)	(165,000)	(151,000)
Net expense	522,000	454,000	1,801,000	1,389,000
Unrecognized compensation cost of awards granted under the plan	3,200,000		3,200,000
Weighted average period over which unrecognized compensation cost is to be recognized (in years)			1.8
Additional disclosures [Abstract]
Weighted average fair value nonvested shares-beginning balance			$ 39.049
Weighted average fair value nonvested shares-granted during the period			$ 51.407
Weighted average fair value nonvested shares-vested during the period			$ 43.300
Weighted average fair value nonvested shares-ending balance	$ 42.901		$ 42.901
Officers and Key Employees [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Number of shares granted during the period, Officers & Key Employees			40,711
Vesting period of shares			3 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)	131,399		131,399
Number of shares awarded during the period			69,271	59,893
Market value of shares awarded			3,700,000	2,300,000
Cost	467,000	407,000	1,399,000	1,221,000
Restricted stock award activity, excluding accrued dividend equivalents [Rolll Forward}
Nonvested shares outstanding, beginning balance			90,688
Granted (in shares)			40,711
Vested (in shares)			0
Nonvested shares outstanding, ending balance	131,399		131,399
Officers and Key Employees [Member] \| Grant Date January 2009 [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Shares outstanding (in shares)	37,748		37,748
Fair value per share	$ 39.350		$ 39.350
Expected volatility (in hundredths)			28.60%
Risk-free interest rate (in hundredths)			1.20%
Restricted stock award activity, excluding accrued dividend equivalents [Rolll Forward}
Nonvested shares outstanding, ending balance	37,748		37,748
Additional disclosures [Abstract]
Weighted average fair value nonvested shares-ending balance	$ 39.350		$ 39.350
Officers and Key Employees [Member] \| Grant Date January 2010 [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Shares outstanding (in shares)	52,940		52,940
Fair value per share	$ 39.020		$ 39.020
Expected volatility (in hundredths)			29.00%
Risk-free interest rate (in hundredths)			1.65%
Restricted stock award activity, excluding accrued dividend equivalents [Rolll Forward}
Nonvested shares outstanding, ending balance	52,940		52,940
Additional disclosures [Abstract]
Weighted average fair value nonvested shares-ending balance	$ 39.020		$ 39.020
Officers and Key Employees [Member] \| Grant Date January 2011 [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Shares outstanding (in shares)	40,711		40,711
Fair value 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 [Rolll Forward}
Nonvested shares outstanding, ending balance	40,711		40,711
Additional disclosures [Abstract]
Weighted average fair value nonvested shares-ending balance	$ 50.940		$ 50.940
Director [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Number of shares granted during the period, Officers & Key Employees			12,220	16,700
Shares Vested, Directors (in hundredths)	100.00%		100.00%
Shares outstanding (in shares)	30,088		30,088
Market value of shares awarded			600,000	600,000
Cost	$ 110,000	$ 97,000	$ 567,000	$ 319,000
Restricted stock award activity, excluding accrued dividend equivalents [Rolll Forward}
Nonvested shares outstanding, beginning balance			25,390
Granted (in shares)			12,220	16,700
Vested (in shares)			(7,522)
Nonvested shares outstanding, ending balance	30,088		30,088
Director [Member] \| Grant Date January 2009 [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Shares outstanding (in shares)	6,952		6,952
Fair value per share	$ 40.265		$ 40.265
Expected volatility (in hundredths)			0.00%
Risk-free interest rate (in hundredths)			0.00%
Restricted stock award activity, excluding accrued dividend equivalents [Rolll Forward}
Nonvested shares outstanding, ending balance	6,952		6,952
Additional disclosures [Abstract]
Weighted average fair value nonvested shares-ending balance	$ 40.265		$ 40.265
Director [Member] \| Grant Date January 2010 [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Shares outstanding (in shares)	13,360		13,360
Fair value per share	$ 37.825		$ 37.825
Expected volatility (in hundredths)			0.00%
Risk-free interest rate (in hundredths)			0.00%
Restricted stock award activity, excluding accrued dividend equivalents [Rolll Forward}
Nonvested shares outstanding, ending balance	13,360		13,360
Additional disclosures [Abstract]
Weighted average fair value nonvested shares-ending balance	$ 37.825		$ 37.825
Director [Member] \| Grant Date January 2011 [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Shares outstanding (in shares)	8,554		8,554
Fair value 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 [Rolll Forward}
Nonvested shares outstanding, ending balance	8,554		8,554
Additional disclosures [Abstract]
Weighted average fair value nonvested shares-ending balance	$ 52.940		$ 52.940
Director [Member] \| June 2011 [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Shares outstanding (in shares)	1,222		1,222
Fair value per share	$ 53.170		$ 53.170
Expected volatility (in hundredths)			0.00%
Risk-free interest rate (in hundredths)			0.00%
Restricted stock award activity, excluding accrued dividend equivalents [Rolll Forward}
Nonvested shares outstanding, ending balance	1,222		1,222
Additional disclosures [Abstract]
Weighted average fair value nonvested shares-ending balance	$ 53.170		$ 53.170