Stock-Based Compensation

3 Months Ended

Mar. 31, 2020

Share-based Payment Arrangement, Noncash Expense [Abstract]

A summary of restricted and deferred stock transactions during the three months ended March 31, 2020 is as follows:



	Number of shares
Non-vested stock awards outstanding at January 1, 2020	2,102,654
Awarded:
Time-vesting shares	68,824
Performance-based shares	161,426
Released:
Time-vesting shares	(82,427	)
Performance-based shares	(163,458	)
Forfeitures:
Time-vesting shares	(47,700	)
Performance-based shares	—
Non-vested stock awards outstanding at March 31, 2020	2,039,319

The performance-based share awards are subject to either a market condition or a performance condition. For awards subject to a market condition, the performance metric is the Company's total shareholder return, which includes share price appreciation and dividends paid during the three-year term of the award, measured against a peer group of companies. These awards cliff vest at the end of three years. The number of performance-based shares that will ultimately vest is based on the level of market performance achieved, ranging between 0% and 200% of the shares originally awarded, and are settled in stock.

For awards subject to a performance condition, the performance metric is the Company's average return on invested capital over the three-year term. These awards cliff vest at the end of three years. The number of performance-based shares that will ultimately vest is based on the level of performance achieved, ranging between 0% and 200% of the shares originally awarded, and are settled in stock.

The time-vesting restricted and deferred stock awards vest ratably over three to five years.

The weighted average grant-date fair values of awards issued during the three months ended March 31, 2020 were $70.31 for the time-vesting stock awards and $72.47 for the performance-based stock awards.

The fair value of the performance-based shares subject to a market condition awarded in 2020 was calculated using a Monte Carlo valuation model, including a weighted average stock price volatility of 22.0%, an expected term of three years, and a weighted average risk-free interest rate of 1.60%.

As of March 31, 2020, unrecognized compensation cost related to outstanding non-vested stock awards was $70. The weighted average period over which the expense is expected to be recognized is 2.83 years. The aggregate market value of the shares released on the vesting dates was $12 for the three months ended March 31, 2020.