Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2020

Share-based Payment Arrangement, Noncash Expense [Abstract]

Target grants performance share

Target grants of performance shares outstanding at December 31, 2020, were as follows:

Grant Date	Performance Period	Target Grant of Shares
February 2019	2019-2021	327,194
February 2020	2020-2022	285,980

Schedule of share-based payment award, performance shares, valuation assumptions

Assumptions used for grants applicable to the market condition for certain performance shares issued in 2020, 2019 and 2018 were:

				2020					2019					2018
Weighted average grant-date fair value				$40.75					$35.07					$34.55
Blended volatility range	15.30	%	–	15.97	%	19.50	%	–	19.69	%	17.87	%	–	22.14	%
Risk-free interest rate range	1.45	%	–	1.62	%	2.46	%	–	2.55	%	1.86	%	–	2.46	%
Weighted average discounted dividends per share				$2.91					$2.85					$2.46

Summary of the status of the performance share awards

A summary of the status of the performance share awards for the year ended December 31, 2020, was as follows:

	Number of Shares	Weighted Average Grant-Date Fair Value
Nonvested at beginning of period	573,503	$	30.81
Granted	285,980	36.19
Additional performance shares earned	123,147	27.48
Less:
Vested	369,456	29.84
Nonvested at end of period	613,174	$	33.24