Stock Benefit Plans (Tables)

12 Months Ended

Dec. 31, 2020

Share-based Payment Arrangement [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 2020, 2019 and 2018 are as follows:

	2020		2019		2018
Risk-free interest rate	1.44	%	2.51	%	2.73	%
Expected life (in years)	6.0		6.0		6.0
Expected volatility	20.33	%	20.93	%	23.23	%
Expected dividend yield	1.53	%	1.82	%	1.81	%

The assumptions used in the Monte Carlo simulation model for PSU's granted with the TSR modifier by the Company in 2020 include:

	2020
Risk-Free Interest Rate	1.39	%
Dividend Yield	1.8	%
Volatility	16.0	%
Initial TSR	7.9	%

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, 2020 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, 2020	8,859,128	$	64.69
Granted	1,326,790	$	118.87
Exercised	(2,348,898)	$	44.72
Forfeited	(67,125)	$	96.09
Balance at December 31, 2020	7,769,895	$	79.71	6.5 years	$	285,520
Options vested or expected to vest at December 31, 2020	7,645,454	$	79.45	6.5 years	$	282,844
Options exercisable at December 31, 2020	4,299,859	$	64.71	5.2 years	$	220,402

Summary of restricted stock units and performance stock units

A summary of the status of the Company's RSU and PSU awards as of December 31, 2020 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, 2020	5,957,737	$	87.80	650,547	$	82.75
Granted	2,156,602	$	118.20	235,432	$	127.71
Vested	(2,291,265)	$	82.96	(210,950)	$	73.20
Forfeited	(309,393)	$	96.28	(18,347)	$	97.02
Non-vested balance at December 31, 2020	5,513,681	$	101.22	656,682	$	101.54