authorized for grant under the 2013 Plan and 4,071,139 shares were available for future equity grants. Non-performance and performance-based awards issued under the 2013 Plan have a time-based vesting ranging from one to three years. All options issued under the 2013 Plan have a term of ten years from the date of grant. Under the terms of the 2013 Plan, all equity awards granted thereunder are subject to a one year minimum vesting period.
A summary of the status of non-vested restricted shares at June 30, 2017 and changes during the six months ended June 30, 2017 is as follows:
Non-vested awards at December 31, 2016
Non-vested awards at June 30, 2017
A summary of stock option activity for the six months ended June 30, 2017 is summarized as follows:
Term (in years)
Outstanding at December 31, 2016
Options exercised with total intrinsic value of $12.0 million
Outstanding at June 30, 2017 with an aggregate intrinsic value of $138.5 million
Vested and Exercisable at June 30, 2017 with an aggregate intrinsic value of $138.3 million
The aggregate intrinsic value represents the total pre-tax intrinsic value received by the option holders on the exercise date or that would have been received by the option holders had all holders of in-the-money outstanding options at June 30, 2017 exercised their options at the Company’s closing stock price on June 30, 2017.
The fair value of each stock option award converted as part of the Merger was calculated on the merger date, December 1, 2016, using the Black-Scholes valuation model with the following assumptions indicated in the below table. The volatility assumptions were based on the historical stock volatility of the Company.
Risk free rate
0.82% - 1.90%
Expected term of options in years
1.0 - 5.0
Expected dividend yield
Other information pertaining to share-based activity during the three and six months ended June 30, 2017 and 2016 is as follows (in millions):
Three Months Ended June 30,
Six Months Ended June 30,
Share-based compensation expense from continuing operations
Fair value of shares vested
Cash received from option exercises
Tax expense (benefit) from exercises of share based awards