Common Stock (Tables)

9 Months Ended

Sep. 30, 2011

Common Stock [Abstract]

Assumptions used for calculating the fair values of stock option awards

	Nine Months
	Ended
	September 30,
	2011			2010
Stock Options Granted
Weighted average grant date fair value, per share	$	26.13		$	11.76
Weighted average assumptions used:
Expected volatility		70.1	%		75.4	%
Expected lives		4.8			4.6
Risk-free interest rates		1.8	%		2.2	%
Dividend yields		0.0	%		0.0	%

Stock options status and activity

	Nine Months Ended September 30, 2011
						Weighted Avg.
	Shares			Weighted Avg.		Remaining		Aggregate
	Under			Exercise		Life in		Intrinsic
	Option			Prices		Years		Value
								(Millions)
Outstanding Stock Options
Outstanding, January 1, 2011		3,129,241		$	14.43		4.3	$	68
Granted		201,133			45.42
Expired		(56,046	)		3.66
Forfeited		(13,184	)		9.36
Exercised		(125,624	)		17.10				3
Outstanding, March 31, 2011		3,135,520		$	16.53		4.4	$	80
Granted		2,711			43.51
Forfeited		(23,841	)		14.26
Exercised		(82,166	)		11.50				3
Outstanding, June 30, 2011		3,032,224		$	16.71		4.2	$	76
Granted		1,649			44.02
Forfeited		(450	)		4.03
Exercised		(115,249	)		8.94				3
Outstanding, September 30, 2011		2,918,174		$	17.03		4.0	$	54

Nonvested restricted shares

	Nine Months Ended
	September 30, 2011
				Weighted Avg.
				Grant Date
	Shares			Fair Value
Nonvested Restricted Shares
Nonvested balance at January 1, 2011		558,198		$	11.58
Granted		141,036			45.42
Vested		(268,891	)		12.00
Forfeited		(4,822	)		13.74
Nonvested balance at March 31, 2011		425,521		$	22.51
Granted		1,381			43.51
Vested		(3,851	)		15.47
Forfeited		(7,190	)		23.82
Nonvested balance at June 30, 2011		415,861		$	22.62
Granted		1,042			44.02
Vested		(3,206	)		15.41
Forfeited		(158	)		1.86
Nonvested balance at September 30, 2011		413,539		$	22.74