Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2011

Assumptions

Assumptions	2011	2010	2009
Risk-free interest rate	0.9%	2.0%	2.2%
Expected dividend yield	0	0	0
Expected volatility	58.1%	60.1%	61.6%
Expected term	5 years	5 years	5 years

Summary of Stock Option Activity, Options Outstanding

	2011		2010		2009
		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	4,769,122	$     16.13	5,649,233	$     11.59	7,396,537	$       7.44
Granted	853,478	36.64	446,895	37.05	412,515	39.83
Exercised	(850,659)	7.54	(1,293,046)	3.01	(2,152,819)	2.67
Forfeited or expired	(30,209)	35.46	(33,960)	35.26	(7,000)	31.21
Options outstanding at December 31	4,741,732	$     21.24	4,769,122	$     16.13	5,649,233	$     11.59

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

	Options Outstanding				Options Exercisable
			Weighted				Weighted
			Average				Average
		Weighted	Remaining	Aggregate		Weighted	Remaining	Aggregate
	Options	Average	Contractual	Intrinsic	Options	Average	Contractual	Intrinsic
Range of	Outstanding at	Exercise	Life	Value	Exercisable at	Exercise	Life	Value
Exercise Prices	December 31, 2011	Price	(Years)	(in thousands)	December 31, 2011	Price	(Years)	(in thousands)
$1.43 - $3.10	1,727,398	$    2.10	1.5		1,727,398	$    2.10	1.5
$3.11 - $30.00	862,650	22.19	2.1		856,544	22.14	2.1
$30.01 - $36.00	606,133	31.54	4.4		490,190	31.11	4.0
$36.01 - $40.00	1,130,705	36.77	6.5		153,086	36.86	5.5
$40.01 - $51.47	414,846	41.60	5.0		254,850	41.50	4.8
	4,741,732	$  21.24	3.5	$  60,505	3,482,068	$  15.53	2.4	$ 60,484

Summary of Restricted Stock Activity and Unvested Shares

	2011		2010		2009
		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	834,058	$     36.24	794,529	$     33.70	843,430	$     27.66
Granted	532,754	36.41	390,415	36.46	319,950	39.03
Vested	(294,358)	34.90	(319,894)	30.45	(359,247)	24.37
Forfeited	(52,717)	36.45	(30,992)	33.54	(9,604)	29.47
Unvested shares at December 31	1,019,737	$     36.71	834,058	$     36.24	794,529	$     33.70

Stock Options [Member]

Employee Stock-Based Compensation Costs Table

	2011	2010	2009
	(in thousands)
Stock-based compensation cost related to stock options – general and administrative expense	$            4,959	$            4,706	$            5,108
Stock-based compensation cost related to stock options – capitalized	$            3,365	$            2,679	$            2,124

Restricted Stock [Member]

Employee Stock-Based Compensation Costs Table

	2011	2010	2009
	(in thousands)
Stock-based compensation cost related to restricted stock grants – general and administrative expense	$            5,591	$            5,114	$            5,069
Stock-based compensation cost related to restricted stock grants – capitalized	$            5,162	$            4,107	$            3,767