Equity Based Compensation Plans (Details) (USD $)	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Equity Based Compensation Plans [Abstract]
Number of shares available (in shares)	1,200,000
Exercise price as a percentage of fair market value of common stock on grant date, minimum (in hundredths)	100.00%
Life of options, minimum	7 years
Life of options, maximum	10 years
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 4,141,000	$ 2,927,000	$ 3,251,000
Intrinsic value of the options outstanding and fully vested	9,900,000	10,600,000	7,700,000
Average fair value of stock options granted (in dollars per share)	$ 12.64	$ 14.49	$ 18.39
Cap on the appreciation of the market price over the exercise price	100	75
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option grants to officers and employees vesting period	1 year
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option grants to officers and employees vesting period	5 years
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	2,000,000	1,500,000	1,000,000
Stock-based compensation capitalized	300,000	200,000	200,000
Intrinsic value of options exercised	2,900,000	3,800,000	2,900,000
Unrecognized compensation cost	3,200,000
Unrecognized compensation cost, weighted average recognition period, minimum	1 year
Unrecognized compensation cost, weighted average recognition period, maximum	5 years
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	2,000,000	1,500,000	1,000,000
Stock-based compensation capitalized	300,000	200,000	200,000
Unrecognized compensation cost	1,900,000
Series Z Incentive Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	2,100,000	1,500,000	2,300,000
Stock-based compensation capitalized	500,000	300,000	600,000
Intrinsic value of options exercised	20,800,000
Unrecognized compensation cost	$ 7,300,000
Unrecognized compensation cost, weighted average recognition period, maximum	14 years
Series Z Incentive Units [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option grants to officers and employees vesting period	8 years
Series Z Incentive Units [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option grants to officers and employees vesting period	15 years

Cap on the appreciation of the market price over the exercise price.

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The minimum acceptable exercise price as a percentage of fair market value of common stock on grant date.

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The term of the options granted, maximum.

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The term of the options granted, minimum.

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The maximum 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 minimum 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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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.

+ References

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As of the balance sheet date, the aggregate unrecognized cost of equity-based awards made to employees under equity-based compensation awards that have yet to vest.

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- Definition

The aggregate amount of noncash, equity-based employee remuneration. This may include the value of stock or unit options, amortization of restricted stock or units, and adjustment for officers' compensation. As noncash, this element is an add back when calculating net cash generated by operating activities using the indirect method.

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Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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The total accumulated difference between fair values of underlying shares on dates of exercise and exercise price on options which were exercised (or share units converted) into shares during the reporting period under the plan.

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The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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Amount of difference between fair value of the underlying shares reserved for issuance and exercise prices of fully vested and expected to vest options outstanding.

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