Common Stock (Tables)

3 Months Ended

Mar. 31, 2014

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

Assumptions Used for Calculating Fair Values of Stock Option Awards

The fair value of share-based awards is determined at the time the awards are granted which is generally in January of each year, and requires judgment in estimating employee and market behavior.

	Three Months Ended March 31,
	2014			2013
Stock Options Granted
Weighted average grant date fair value, per share	$	26.46		$	19.84
Weighted average assumptions used:
Expected volatility	52.8		%	66.4		%
Expected lives	5.0			4.9
Risk-free interest rates	1.7		%	0.7		%
Dividend yields	—		%	—		%

Stock Options Status and Activity

Stock Options — The following table reflects the status and activity for all options to purchase common stock for the period indicated:

	Three Months Ended March 31, 2014
	Shares Under Option		Weighted Avg. Exercise Prices		Weighted Avg. Remaining Life in Years	Aggregate Intrinsic Value
						(Millions)
Outstanding Stock Options
Outstanding, January 1, 2014	1,983,573		$	22.93	4.5	$	62
Granted	192,624		56.23
Canceled	(31,299	)	19.78
Forfeited	(300	)	22.77
Exercised	(25,595	)	14.72			1
Outstanding, March 31, 2014	2,119,003		$	26.10	4.6	$	67

Nonvested Restricted Shares

Restricted Stock — The following table reflects the status for all nonvested restricted shares for the period indicated:

	Three Months Ended March 31, 2014
	Shares		Weighted Avg. Grant Date Fair Value
Nonvested Restricted Shares
Nonvested balance at January 1, 2014	368,268		$	34.90
Granted	131,561		54.90
Vested	(186,112	)	36.57
Forfeited	—		—
Nonvested balance at March 31, 2014	313,717		$	42.30