At March 31, 2019, we had two shareholder approved stock incentive plans under which share based grants were outstanding. We were originally authorized to issue up to 1.6 million shares and 1.0 million shares under our 2005 Stock Incentive Plan and 2014 Stock Incentive Plan, respectively. At March 31, 2019, approximately 0.3 million shares were authorized for future use under those plans.

Share-based compensation activity during the three months ended March 31, 2019 included the following:

(Shares in thousands)	Granted		Vested
Restricted Stock Units (RSUs)		47,350		1,000
Performance Share Awards (PSAs)		142,066		—

A total of 0.3 million shares of common stock were issued during the three months ended March 31, 2019 as a result of RSU and PSA vesting during 2018 and 2019.

The following table details equity-based compensation expense and the related income tax benefit.

	Three Months Ended March 31,
(in thousands)	2019		2018
Equity-based compensation expense:
Performance share awards	$	1,044	$	936
Restricted stock units		557		480
Deferred compensation stock equivalent units expense		16		185
Accelerated share-based termination benefits in connection with the merger		—		1,678
Total equity-based compensation expense	$	1,617	$	3,279

Total tax benefit recognized for share-based expense	$	72	$	111

PSAs granted under the stock incentive plans have a three-year performance period and shares are issued at the end of the period if the performance measures are met. The performance measures are based on the percentile ranking of our total shareholder return relative to the total shareholder return performance of both a selected peer group of companies and a larger group of indexed companies over the three-year performance period. The number of shares actually issued, as a percentage of the amount subject to the PSA, could range from 0% to 200%. PSAs granted under our stock incentive plans do not have voting rights unless and until shares are issued upon settlement. If shares are issued at the end of the three-year performance measurement period, the recipients will receive dividend equivalents in the form of additional shares at the time of payment equal to the dividends that would have been paid on the shares earned had the recipients owned the shares during the three-year period. Therefore, the shares are not considered participating securities. The fair value of performance shares granted in 2019 was $37.87 per share.

The following table presents the key inputs used in the Monte Carlo simulation to calculate the fair value of the performance share awards in 2019:

Stock price as of valuation date	$	35.01
Risk-free rate		2.47	%
Expected volatility		25.15	%
Expected dividend yield (assuming full reinvestment)		—
Expected term (years)		3.00

RSU awards accrue dividend equivalents based on dividends paid during the RSU vesting period. The dividend equivalents will be converted into additional RSUs that will vest in the same manner as the underlying RSUs to which they relate. Therefore, the shares are not considered participating securities. The terms of the awards state that the RSUs will vest in a given time period of one to three years and the terms of certain awards follow a vesting schedule within the given time period. The weighted average fair value of the RSUs granted in 2019 was $35.01 which equaled our common share price on the date of grant.