Common Stock (Tables)

6 Months Ended

Jun. 30, 2013

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.

	Six Months Ended June 30,
	2013			2012
Stock Options Granted
Weighted average grant date fair value, per share	$	19.84		$	17.35
Weighted average assumptions used:
Expected volatility	66.4		%	73.5		%
Expected lives	4.9			4.7
Risk-free interest rates	0.7		%	0.8		%
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:

	Six Months Ended June 30, 2013
	Shares Under Option		Weighted Avg. Exercise Prices		Weighted Avg. Remaining Life in Years	Aggregate Intrinsic Value
						(Millions)
Outstanding Stock Options
Outstanding, January 1, 2013	2,447,475		$	20.14	4.1	$	29
Granted	311,539		36.29
Canceled	(7,225	)	11.73
Forfeited	(14,920	)	14.59
Exercised	(82,622	)	19.96			1
Outstanding, March 31, 2013	2,654,247		$	22.12	4.3	$	41
Granted	388		38.90
Forfeited	(450	)	21.81
Exercised	(393,442	)	22.53			7
Outstanding, June 30, 2013	2,260,743		22.06		4.7	44

Nonvested Restricted Shares

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

	Six Months Ended June 30, 2013
	Shares		Weighted Avg. Grant Date Fair Value
Nonvested Restricted Shares
Nonvested balance at January 1, 2013	348,918		$	31.69
Granted	204,731		36.28
Vested	(154,160	)	29.54
Forfeited	—		—
Nonvested balance at March 31, 2013	399,489		$	34.88
Granted	226		38.90
Vested	(15,289	)	35.40
Forfeited	—		—
Nonvested balance at June 30, 2013	384,426		34.86