Stock Benefit Plans (Tables)

12 Months Ended

Dec. 31, 2017

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 2017, 2016 and 2015 are as follows:

	2017	2016	2015
Risk-free interest rate	2.09%	1.39%	1.78%
Expected life (in years)	6.0	6.0	6.0
Expected volatility	23.23%	25.55%	23.75%
Expected dividend yield	1.86%	2.15%	1.97%

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, 2017 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, 2017	13,242,529		$	39.15
Granted	1,710,853		$	73.20
Exercised	(4,258,027	)	$	30.42
Forfeited	(494,653	)	$	62.00
Balance at December 31, 2017	10,200,702		$	47.39	5.9 years	$	351,317
Options vested or expected to vest at December 31, 2017	10,052,720		$	47.17	5.9 years	$	348,494
Options exercisable at December 31, 2017	6,247,224		$	37.75	4.6 years	$	275,398

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, 2017 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, 2017	3,044,029		$	56.40	722,017		$	54.68
Granted	2,610,599		$	73.23	260,387		$	73.20
Vested	(1,307,825	)	$	55.31	(212,458	)	$	48.19
Forfeited	(294,056	)	$	65.06	(79,345	)	$	61.92
Non-vested balance at December 31, 2017	4,052,747		$	66.97	690,601		$	62.82