Stock-Based Compensation (Details) (USD $)	3 Months Ended	6 Months Ended
Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Stock-Based Compensation
Stock-based compensation costs - general and administrative expense	$ 2,236,000	$ 2,136,000	$ 4,686,000	$ 4,433,000
Stock-based compensation costs - capitalized	1,905,000	1,689,000	3,815,000	3,397,000
Unrecognized compensation cost related to unvested stock option and restricted stock grants	$ 31,800,000		$ 31,800,000
Weighted average period over which cost is recognized, years			2.4
Stock options, outstanding at December 31, number of options			4,769,122
Stock options, granted, number of options			15,000
Stock options, exercised, number of options			(397,640)
Stock options, forfeited or expired, number of options			(17,001)
Stock options, outstanding at June 30, number of options	4,369,481		4,369,481
Stock options, exercisable at June 30, 2011	3,546,494		3,546,494
Stock options, outstanding at December 31, weighted average exercise price			$ 16.13
Stock options, granted, weighted average exercise price	$ 40.63		$ 40.63
Stock options, exercised, weighted average exercise price	$ 8.46		$ 8.46
Stock options, forfeited or expired, weighted average exercise price			$ 37.46
Stock options, outstanding at June 30, weighted average exercise price	$ 16.83		$ 16.83
Stock options exercisable at June 30 2011, weighted average exercise price	$ 12.16		$ 12.16
Restricted Stock, Unvested shares at December 31, Number of Shares			834,058
Restricted Stock, Granted, Number of Shares			1,270
Restricted Stock, Vested, Number of Shares			(25,818)
Restricted Stock, Forfeited, Number of Shares			(29,729)
Restricted Stock, Unvested shares at June 30, Number of Shares	779,781		779,781
Restricted Stock, Unvested shares at December 31, Weighted Average Grant Date Fair Value			$ 36.24
Restricted Stock, Vested, Weighted Average Grant Date Fair Value			$ 39.00
Restricted Stock, Granted, Weighted Average Grant Date Fair Value			$ 38.58
Restricted Stock, Forfeited, Weighted Average Grant Date Fair Value	$ 36.49		$ 36.49
Restricted Stock, Unvested shares at June 30, Weighted Average Grant Date Fair Value	$ 36.15		$ 36.15

Number of stock options exercised in the current period.

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The weighted average price as of the beginning of the year at which grantees can acquire the shares reserved for issuance under the stock option plan.

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As of the latest balance sheet date presented, the total compensation cost related to outstanding, nonvested share-based compensation awards not yet recognized (will be recogized as services are performed or other vesting criteria are met).

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Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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Represents the compensation cost capitalized during the period arising from equity-based compensation arrangements (for example, shares of stock, units, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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The weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, using a decimal to express in number of years.

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The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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The weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect during the reporting period as a result of the occurrence of a terminating event specified in the contractual agreement of the plan.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.

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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

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The weighted average price at which option holders acquired shares when converting their stock options into shares under the plan during the reporting period.

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For presentations that combine terminations, the number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan or that expired.

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The combined weighted average exercise price associated with stock options during the period that have either lapsed or been forfeited.

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Net number of share options (or share units) granted during the period.

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The weighted average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on stock options awarded under the plan during the reporting period.

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The number of shares reserved for issuance under stock option agreements awarded under the plan that validly exist and are outstanding as of the balance sheet date, including vested options.

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