Share-Based Compensation Plans

The following table summarizes share-based compensation expense recognized in the Condensed Consolidated Statements of Income in Compensation and benefits (in millions):



	Three months ended September 30				Nine months ended September 30
	2017		2016		2017		2016
Restricted share units (“RSUs”)	$	42	$	40	$	143	$	136
Performance share awards (“PSAs”)	22		24		63		67
Employee share purchase plans	3		2		8		7
Total share-based compensation expense	$	67	$	66	$	214	$	210

Restricted Share Units

RSUs generally vest between three and five years. The fair value of RSUs is based upon the market value of Aon ordinary shares at the date of grant. With certain limited exceptions, any break in continuous employment will cause the forfeiture of all non-vested awards. Compensation expense associated with RSUs is recognized on a straight-line basis over the requisite service period. Dividend equivalents are paid on certain RSUs, based on the initial grant amount.

The following table summarizes the status of the Company’s RSUs (shares in thousands):



	2017				2016
	Shares		Fair Value ⁽¹⁾		Shares		Fair Value ⁽¹⁾
Non-vested at December 31	6,195		$	89	7,167		$	77
Granted	1,549		122		2,110		101
Vested	(2,294	)	82		(2,729	)	70
Forfeited	(590	)	92		(333	)	81
Non-vested at September 30	4,860		$	102	6,215		$	88


(1)	Represents per share weighted average fair value of award at date of grant.

Unamortized deferred compensation expense amounted to $367 million as of September 30, 2017, with a remaining weighted-average amortization period of approximately 2.1 years.

Performance Share Awards

The vesting of PSAs is contingent upon meeting a cumulative level of earnings per share performance over a three-year period. The actual issue of shares may range from 0-200% of the target number of PSAs granted, based on the terms of the plan and level of achievement of the related performance target. The grant date fair value of PSAs is based upon the market price of Aon ordinary shares at the date of grant. The performance conditions are not considered in the determination of the grant date fair value for these awards. Compensation expense is recognized over the performance period based on management’s estimate of the number of units expected to vest. Management evaluates its estimate of the actual number of shares expected to be issued at the end of the programs on a quarterly basis. The cumulative effect of the change in estimate is recognized in the period of change as an adjustment to Compensation and benefits expense, if necessary. Dividend equivalents are not paid on PSAs.

Information as of September 30, 2017 regarding the Company’s target PSAs granted and shares that would be issued at current performance levels for PSAs granted during the nine months ended September 30, 2017 and the years ended December 31, 2016 and 2015, respectively, is as follows (shares in thousands and dollars in millions, except fair value):



	September 30, 2017		December 31, 2016		December 31, 2015
Target PSAs granted during period	548		752		967
Weighted average fair value per share at date of grant	$	114	$	100	$	96
Number of shares that would be issued based on current performance levels	544		663		1,362
Unamortized expense, based on current performance levels	$	51	$	27	$	11