Stock Option Plans (Tables)

6 Months Ended

Jun. 30, 2019

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

Stock Options Issued

The following table summarizes the assumptions used in the valuation of the 2018 and 2019 option grants. During the six months ended June 30, 2019, stock option expense totaling $970,500 was included in general and administrative expense in the Consolidated Statements of Operations. As of June 30, 2019, the estimated future expense related to unvested stock options was $3.2 million.

	Directors						Officers
Grant date	May 11, 2018			May 3, 2019			May 11, 2018			May 3, 2019
Exercise price	$	49.46		$	55.71		$	49.46		$	55.71
Volatility	0.192			0.236			0.177			0.206
Expected life (years)	5.0			5.0			7.0			7.0
Assumed yield	3.70		%	3.75		%	3.75		%	3.80		%
Risk-free rate	2.84		%	2.33		%	2.94		%	2.43		%

Summary of Option Activity

The table below summarizes the option activity for the six months ended June 30, 2019:

	Number of Shares		Weighted Average Exercise Price per share		Aggregate Intrinsic Value
Outstanding at January 1	1,114,169		$	52.40	$	543,662
Granted	260,000		55.71		—
Exercised	(46,055	)	45.07		503,262
Expired/Forfeited	(7,500	)	56.07		—
Outstanding at June 30	1,320,614		53.29		4,728,314
Exercisable at June 30	774,614		52.28		3,640,270