Stock Compensation Plan (Tables)

3 Months Ended

Mar. 31, 2018

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

Schedule of stock options awarded

The following table presents information regarding Options awarded during the three months ended March 31, 2018: 

Options granted	108,420
Per share weighted average exercise price	$	93.22
Per share weighted average grant date fair value	$	15.00

Schedule of assumptions used to determine the grant date fair value of options granted

The weighted-average grant date fair value for Options granted during the three months ended March 31, 2018 was estimated using the Black-Scholes option valuation model with the following assumptions: 

Expected term in years	5.7
Risk free interest rate	2.5	%
Volatility	21.5	%
Dividend yield	3.0	%

Schedule of stock options vested during the period

The following table presents information regarding Options that vested during the three months ended March 31, 2018: 

Options vested	100,652
Aggregate grant date fair value of Options vested (in millions)	$	1.4

Schedule of outstanding stock options

The following table presents information regarding outstanding Options:

	March 31, 2018		December 31, 2017
Options outstanding	537,246		464,958
Aggregate intrinsic value (in millions)	$	10.0	$	16.3
Per share weighted average exercise price	$	63.85	$	55.60
Exercisable Options	307,043		241,944
Aggregate intrinsic value (in millions)	$	9.2	$	12.1
Unvested Options	230,203		223,014
Per share weighted average grant date fair value	$	14.23	$	13.87