STOCK-BASED COMPENSATION (Tables)

12 Months Ended

Dec. 31, 2012

Disclosure Of Compensation Related Costs, Share-Based Payments [Abstract]

Total Stock-Based Compensation Expense

Total stock-based compensation expense in our Consolidated Statements of Income during the twelve months ended December 31, 2012, 2011 and 2010, was as follows:

	Twelve Months Ended December 31,
(in millions)	2012		2011		2010
Cost of services	$	3.9	$	3.6	$	3.6
Selling, general and administrative expenses		24.1		20.8		18.2
Stock-based compensation expense, before income taxes	$	28.0	$	24.4	$	21.8

Assumptions Used to Estimate Fair Value of Stock Options Granted

The fair value for stock options granted during the twelve months ended December 31, 2012, 2011 and 2010, was estimated at the date of grant, using the binomial model with the following weighted-average assumptions:

	Twelve Months Ended December 31,
	2012			2011			2010
Dividend yield		1.8	%		1.8	%		0.5	%
Expected volatility		31.9	%		32.7	%		29.9	%
Risk-free interest rate		0.6	%		1.2	%		1.6	%
Expected term (in years)		4.9			4.8			4.6
Weighted-average fair value of stock options granted	$	10.67		$	7.85		$	8.28

Changes in Outstanding Options and Weighed-Average Exercise Price Per Share

The following table summarizes changes in outstanding stock options during the twelve months ended December 31, 2012, as well as stock options that are vested and expected to vest and stock options exercisable at December 31, 2012: 

						Weighted-Average
				Weighted-Average		Remaining		Aggregate
	Shares			Exercise Price		Contractual Term		Intrinsic Value
	(in thousands)					(in years)		(in millions)
Outstanding at December 31, 2011		6,715		$	31.82
Granted (all at market price)		501		$	47.04
Exercised		(2,352	)	$	29.37
Forfeited and cancelled		(116	)	$	31.85
Outstanding at December 31, 2012		4,748		$	34.64		6.5	$	92.5
Vested and expected to vest at December 31, 2012		4,563		$	34.58		6.4	$	89.2
Exercisable at December 31, 2012		3,061		$	33.34		5.3	$	63.6

The following table summarizes changes in outstanding options and the related weighted-average exercise price per share for the twelve months ended December 31, 2011 and 2010:

	December 31,
	2011					2010
	Shares			Weighted- Average Price		Shares			Weighted- Average Price
	(Shares in thousands)					(Shares in thousands)
Outstanding at the beginning of the year		6,526		$	30.63		6,845		$	28.68
Granted (all at market price)		1,298		$	32.94		1,216		$	32.02
Exercised		(947	)	$	25.02		(1,358	)	$	21.58
Forfeited and cancelled		(162	)	$	32.99		(177	)	$	34.04
Outstanding at the end of the year		6,715		$	31.82		6,526		$	30.63
Exercisable at end of year		4,289		$	31.71		4,248		$	30.28

Summary of Changes in Nonvested Stock and Weighted-Average Grant Date Fair Value

The following table summarizes changes in our nonvested stock during the twelve months ended December 31, 2012, 2011 and 2010 and the related weighted-average grant date fair value:

				Weighted-Average
				Grant Date
	Shares			Fair Value
	(in thousands)
Nonvested at December 31, 2009		1,110		$	33.10
Granted		553		$	33.27
Vested		(317	)	$	38.08
Forfeited		(36	)	$	33.20
Nonvested at December 31, 2010		1,310		$	31.54
Granted		513		$	34.07
Vested		(340	)	$	34.34
Forfeited		(52	)	$	30.70
Nonvested at December 31, 2011		1,431		$	31.79
Granted		685		$	44.59
Vested		(440	)	$	29.02
Forfeited		(60	)	$	33.31
Nonvested at December 31, 2012		1,616		$	37.95