Stock Benefit Plans (Tables)

12 Months Ended

Dec. 31, 2018

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

Option pricing valuation model for options granted

The assumptions used in the Black-Scholes option pricing valuation model for options granted by the Company in 2018, 2017 and 2016 are as follows:

	2018		2017		2016
Risk-free interest rate	2.73	%	2.09	%	1.39	%
Expected life (in years)	6.0		6.0		6.0
Expected volatility	23.23	%	23.23	%	25.55	%
Expected dividend yield	1.81	%	1.86	%	2.15	%

Summary of the status of MMC's stock option awards

A summary of the status of the Company’s stock option awards as of December 31, 2018 and changes during the year then ended is presented below:

	Shares		Weighted Average Exercise Price		Weighted Average Remaining Contractual Term	Aggregate Intrinsic Value ($000)
Balance at January 1, 2018	10,200,702		$	47.39
Granted	1,381,391		$	83.05
Exercised	(1,452,879	)	$	33.92
Forfeited	(161,176	)	$	69.64
Balance at December 31, 2018	9,968,038		$	53.94	5.8 years	$	258,062
Options vested or expected to vest at December 31, 2018	9,830,816		53.72		5.8 years	256,622
Options exercisable at December 31, 2018	6,321,055		$	43.78	4.5 years	$	224,687

Summary of restricted stock units and performance stock units

A summary of the status of the Company's restricted stock units and performance stock units as of December 31, 2018 and changes during the period then ended is presented below:

	Restricted Stock Units				Performance Stock Units
	Shares		Weighted Average Grant Date Fair Value		Shares		Weighted Average Grant Date Fair Value
Non-vested balance at January 1, 2018	4,052,747		$	66.97	690,601		$	62.82
Granted	2,390,859		$	83.05	225,736		$	83.05
Vested	(1,796,343	)	$	64.22	(173,978	)	$	57.33
Forfeited	(317,032	)	$	73.81	(43,561	)	$	69.20
Non-vested balance at December 31, 2018	4,330,231		$	76.49	698,798		$	70.33