STOCK-BASED COMPENSATION

12 Months Ended

Dec. 31, 2019

Share-based Payment Arrangement [Abstract]

The Company's 1999 Omnibus Plan, as amended and restated effective June 7, 2018, (the "1999 Plan") is the primary stock compensation plan from which broad-based employee, non-employee director and consultant equity awards may be made. At December 31, 2019, there were 1,833,091 shares of common stock available for future grant under the 1999 Plan. In addition, under plans assumed in connection with various acquisitions, there were 72,006 shares of common stock available for future grant at December 31, 2019.

Stock-based compensation issued under the plans generally consists of restricted stock units, performance share units and, to a far lesser extent and only in the context of assuming grants in connection with acquisitions, stock options. The Company issues shares of common stock upon the vesting of restricted stock units and performance share units and the exercise of stock options. See Note 2 for the Company's accounting policy on stock-based compensation.

Stock-based compensation included in "Personnel" expenses in the Consolidated Statements of Operations was $308 million, $317 million and $261 million for the years ended December 31, 2019, 2018 and 2017, respectively. Stock-based compensation for the years ended December 31, 2019, 2018 and 2017 includes a benefit of $4 million and charges of $48 million and $11 million, respectively, representing the impact of adjusting the estimated probable outcome at the end of the performance period for outstanding unvested performance share units. The related tax benefit for stock-based compensation was $38 million, $36 million and $46 million for the years ended December 31, 2019, 2018 and 2017, respectively.

Share-based awards granted by the Company during the years ended December 31, 2019, 2018 and 2017 had aggregate grant-date fair values of $380 million, $337 million and $304 million, respectively. Restricted stock units and performance share units that vested during the years ended December 31, 2019, 2018, and 2017 had aggregate fair values at vesting of $373 million, $415 million and $251 million, respectively. At December 31, 2019, there was $413 million of total future compensation cost related to unvested share-based awards to be recognized over a weighted-average period of 1.8 years.

Restricted Stock Units

The following table summarizes the activity of restricted stock units for employees and non-employee directors during the years ended December 31, 2017, 2018 and 2019:



Restricted Stock Units	Shares		Weighted-Average Grant Date Fair Value

Unvested at December 31, 2016	195,059			$	1,300

Granted	100,614			$	1,745
Vested	(67,041	)		$	1,302
Forfeited/Canceled	(24,671	)		$	1,430
Unvested at December 31, 2017	203,961			$	1,503

Granted	116,583			$	2,025
Vested	(69,693	)		$	1,389
Forfeited/Canceled	(25,868	)		$	1,731
Unvested at December 31, 2018	224,983			$	1,783

Granted	157,205			$	1,739
Vested	(95,484	)		$	1,653
Forfeited/Canceled	(29,959	)		$	1,812
Unvested at December 31, 2019	256,745			$	1,801

The Company makes broad-based grants of restricted stock units that generally vest during a period of one- to three-years, subject to certain exceptions for terminations other than for "cause," for "good reason" or on account of death or disability.

Performance Share Units

The following table summarizes the activity of performance share units for employees during the years ended December 31, 2017, 2018 and 2019:



Performance Share Units	Shares		Weighted-Average Grant Date Fair Value

Unvested at December 31, 2016	320,547			$	1,288

Granted	73,893			$	1,735
Vested	(76,730	)		$	1,328
Performance Shares Adjustment	19,357			$	1,501
Forfeited/Canceled	(16,332	)		$	1,395
Unvested at December 31, 2017	320,735			$	1,386

Granted	49,721			$	2,034
Vested	(134,549	)		$	1,250
Performance Shares Adjustment	66,245			$	1,872
Forfeited/Canceled	(15,573	)		$	1,685
Unvested at December 31, 2018	286,579			$	1,659

Granted	61,912			$	1,716
Vested	(118,668	)		$	1,346
Performance Shares Adjustment	(683	)		$	1,729
Forfeited/Canceled	(13,057	)		$	1,769
Unvested at December 31, 2019	216,083			$	1,835

The Company grants performance share units to executives and certain other employees, which generally vest at the end of a three-year period, subject to certain exceptions for terminations other than for "cause," for "good reason" or on account of death or disability. Stock-based compensation related to performance share units reflects the estimated probable outcome at the end of the performance period. Performance share units are payable in shares of the Company's common stock upon vesting. The number of shares which ultimately will vest depends on achieving certain performance metrics by the end of the performance period, assuming there is no accelerated vesting for, among other things, a termination of employment under certain circumstances.

The following table summarizes the estimated vesting of performance share units granted in 2019, 2018 and 2017, net of forfeiture and vesting since the respective grant dates, at December 31, 2019:



Performance Share Units, by grant year	2019	2018	2017
Shares probable to be issued	60,588	76,560	78,935
Shares not subject to the achievement of minimum performance thresholds	47,170	29,753	N/A*
Shares that could be issued if maximum performance thresholds are met	121,176	82,126	N/A*

* The performance period for the performance share units granted in 2017 ended on December 31, 2019.

Stock Options

All outstanding employee stock options were assumed in acquisitions, and generally have a term of 10 years from the grant date. At December 31, 2019, all stock options were vested and exercisable. The aggregate intrinsic value of employee stock options exercised during the years ended December 31, 2019, 2018 and 2017 was $20 million, $5 million and $26 million, respectively.

The following table summarizes the activity for stock options during the year ended December 31, 2019:



Employee Stock Options	Number of Shares		Weighted-Average Exercise Price			Aggregate Intrinsic Value (in millions)			Weighted-Average Remaining Contractual Term (in years)
Balance, December 31, 2018	27,263			$	387		$	36	2.8
Exercised	(12,141	)		$	266
Balance, December 31, 2019	15,122			$	484		$	24	2.6
Vested and exercisable at December 31, 2019	15,122			$	484		$	24	2.6