STOCK-BASED COMPENSATION (Tables)

12 Months Ended

Dec. 31, 2015

STOCK-BASED COMPENSATION [Abstract]

Summary of Additional Information Concerning Restricted Stock Units

The following table summarizes additional information concerning restricted stock units at December 31, 2015:

	Restricted Stock Units		Weighted Average Grant Date Fair Value Per Unit
Unvested as of December 31, 2014	562,426		$	23.26
Granted	504,608		21.11
Vested	(341,354	)	24.78
Dividends reinvested	37,353		23.19
Cancelled	(30,277	)	18.66
Unvested as of December 31, 2015	732,756		$	21.37

Summary of Assumptions used in Total Stockholder Return-Based Stock Units Valuation

The following are the key assumptions used in this valuation:

	2015		2014		2013
Risk Free Interest Rate	0.87% - 1.31%		1.07% - 1.09%		0.37% - 0.67%
Expected Stock Price Volatility	23.55% - 27.02%		24.14% - 24.22%		33.36% - 36.11%
Expected Service Period	2.5 - 3.0 years		3.0 years		3.0 years
Expected Dividend Yield (assuming full reinvestment)	—	%	—	%	—	%