STOCK-BASED COMPENSATION (Tables)

12 Months Ended

Dec. 31, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Summary of Additional Information Concerning Restricted Stock Units

The following table summarizes additional information concerning restricted stock units at December 31, 2018:

	Restricted Stock Units		Weighted Average Grant Date Fair Value Per Unit
Unvested as of December 31, 2017	1,125,487		$	19.71
Granted	601,696		16.02
Vested	(170,951	)	21.35
Dividends reinvested	118,797		19.06
Cancelled/forfeited	(197,711	)	20.34
Unvested as of December 31, 2018	1,477,318		$	17.88

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

The following are the key assumptions used in this valuation:

	2018		2017		2016
Risk free interest rate	2.36% - 2.59%		1.42% - 1.99%		0.78% - 1.60%
Expected stock price volatility	28.57% - 30.02%		28.86% - 30.97%		27.40% - 28.42%
Expected service period	2.5 - 3.0 years		2.2 - 3.0 years		2.3 - 3.0 years
Expected dividend yield (assuming full reinvestment)	—	%	—	%	—	%