Stock Plans (Tables)

12 Months Ended

Dec. 31, 2013

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Disclosure of Share-based Compensation Arrangements by Share-based Payment Award [Table Text Block]

Summary stock options activity is presented in the table below:



	Number of Shares		Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (years)	Aggregate Intrinsic Value (thousands)
Balance at December 31, 2012 (1,937,245 shares exercisable)	4,810,816		$	16.73
Granted	317,174		$	45.86
Exercised	(894,498	)	$	15.74
Forfeited	(166,081	)	$	18.14
Balance at December 31, 2013	4,067,411		$	19.16	6.8	$	116,691
Exercisable at December 31, 2013	1,839,633		$	14.02	5.7	$	62,239
Vested and expected to vest at December 31, 2013	3,795,264		$	18.68	6.7	$	110,710

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]

The following table provides the fair value of options granted under the SCP during 2013, 2012 and 2011, together with a description of the assumptions used to calculate the fair value using the Black-Scholes-Merton option-pricing model:



	Year ended December 31,
	2013			2012			2011
Volatility	41.94		%	43.9		%	45.1		%
Risk-free interest rate - weighted average	1.6		%	0.8		%	1.0		%
Risk-free interest rate - range	(a)			0.81% to 1.03%			0.99% to 2.33%
Dividend yield	—		%	—		%	—		%
Assumed forfeitures	8.0		%	8.0		%	8.0		%
Expected lives	5.4 years			5.7 years			5.4 years
Weighted-average fair value (per share)	$	18.43		$	9.46		$	6.85

(a) At the date of grant, the risk free rate for stock options awarded in 2013 was 1.6%.

Schedule of Nonvested Restricted Stock Units Activity [Table Text Block]

Summary restricted stock activity is presented in the table below:



	Number of Shares		Weighted Average Grant Date Fair Value Per Share
Nonvested at December 31, 2012	1,106,129		$	19.73
Granted	155,930		$	43.47
Vested	(195,834	)	$	19.64
Forfeited	(137,237	)	$	20.05
Nonvested at December 31, 2013	928,988		$	23.69

Schedule of Share-based Payment Award, Employee Stock Purchase Plan, Valuation Assumptions [Table Text Block]

The following table provides the weighted-average fair value of the ESPP stock purchase rights during the years ended December 31, 2013, 2012 and 2011 and the assumptions used to calculate the fair value using the Black-Scholes-Merton option-pricing model:



	Year Ended December 31,
	2013			2012			2011
Volatility - weighted average	25.6		%	29.7		%	39.9		%
Volatility - range	20.9% to 29.6%			22.6% to 35.2%			26.5% to 52.5%
Risk-free interest rate - weighted average	0.04		%	0.07		%	0.06		%
Risk-free interest rate - range	0.02% to 0.08%			0.02% to 0.10%			0.02% to 0.11%
Dividend yield	—		%	—		%	—		%
Expected lives	3 months			3 months			3 months
Weighted-average fair value (per share)	$	5.72		$	3.63		$	3.70

- Definition

Tabular disclosure of components of a stock option or other award plan under which equity-based compensation is awarded to employees, typically comprised of the amount of unearned compensation (deferred compensation cost), compensation expense, and changes in the quantity and fair value of the shares (or other type of equity) granted, exercised, forfeited, and issued and outstanding pertaining to that plan. Disclosure may also include nature and general terms of such arrangements that existed during the period and potential effects of those arrangements on shareholders, effect of compensation cost arising from equity-based payment arrangements on the income statement, method of estimating the fair value of the goods or services received, or the fair value of the equity instruments granted, during the period, cash flow effects resulting from equity-based payment arrangements and, for registrants that accelerate vesting of out of the money share options, reasons for the decision to accelerate.

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