Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2012

Schedule Of Risk Free Interest Rate

Assumptions	2012	2011	2010
Risk-free interest rate	0.6%	0.9%	2.0%
Expected dividend yield	–	–	–
Expected volatility	58.2%	58.1%	60.1%
Expected term	5 years	5 years	5 years

Summary of Stock Option Activity, Options Outstanding

	2012			2011			2010
			Weighted			Weighted			Weighted
			Average			Average			Average
	Number		Exercise	Number		Exercise	Number		Exercise
	of Shares		Price	of Shares		Price	of Shares		Price
Options outstanding at January 1	4,741,732	$	21.24	4,769,122	$	16.13	5,649,233	$	11.59
Granted	613,120		34.34	853,478		36.64	446,895		37.05
Exercised	(1,607,784)		5.71	(850,659)		7.54	(1,293,046)		3.01
Forfeited or expired	(97,548)		37.76	(30,209)		35.46	(33,960)		35.26
Options outstanding at December 31	3,649,520	$	29.84	4,741,732	$	21.24	4,769,122	$	16.13

Schedule of Share-based Compensation, Shares Authorized under Stock Option Plans, by Exercise Price Range [Table Text Block]

	Options Outstanding						Options Exercisable
				Weighted							Weighted
				Average							Average
	Options		Weighted	Remaining		Aggregate		Options		Weighted	Remaining		Aggregate
	Outstanding at		Average	Contractual		Intrinsic		Exercisable at		Average	Contractual		Intrinsic
Range of	December 31,		Exercise	Life		Value		December 31,		Exercise	Life		Value
Exercise Prices	2012		Price	(Years)		(thousands)		2012		Price	(Years)		(thousands)
$1.43 - $3.10	465,772	$	2.64	0.9				465,772	$	2.64	0.9
$16.75 - $29.69	553,756		24.32	1.7				541,606		24.24	1.6
$30.23 - $35.91	1,175,749		33.04	5.2				505,485		31.30	3.1
$36.22 - $39.68	1,062,788		36.77	5.5				493,943		36.75	5.3
$40.15 - $51.47	391,455		41.60	4.0				365,732		41.49	3.9
	3,649,520	$	29.84	4.1	$	20,521		2,372,538	$	26.77	2.9	$	20,437

Summary of Restricted Stock Activity and Unvested Shares

	2012			2011			2010
			Weighted			Weighted			Weighted
			Average			Average			Average
	Number		Grant Date	Number		Grant Date	Number		Grant Date
	of Shares		Fair Value	of Shares		Fair Value	of Shares		Fair Value
Unvested shares at January 1	1,019,737	$	36.71	834,058	$	36.24	794,529	$	33.70
Granted	537,244		34.39	532,754		36.41	390,415		36.46
Vested	(344,164)		36.50	(294,358)		34.90	(319,894)		30.45
Forfeited	(95,302)		36.97	(52,717)		36.45	(30,992)		33.54
Unvested shares at December 31	1,117,515	$	35.64	1,019,737	$	36.71	834,058	$	36.24

Stock Options [Member]

Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Text Block]

	2012		2011		2010
		(in thousands)
Stock-based compensation cost related to stock options – general and administrative expense	$	5,427	$	4,959	$	4,706
Stock-based compensation cost related to stock options – capitalized	$	4,468	$	3,365	$	2,679

Restricted Stock [Member]

Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Text Block]

		2012		2011		2010
		(in thousands)
Stock-based compensation cost related to restricted stock grants – general and administrative expense	$	6,368	$	5,591	$	5,114
Stock-based compensation cost related to restricted stock grants – capitalized	$	5,994	$	5,162	$	4,107