Share Based Compensation (Details Textual) (USD $)	3 Months Ended	6 Months Ended
Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Employee Service Share Based Compensation Allocation of Recognized Period Costs (Textuals)
Share-based compensation expenses			$ 5,939,000	$ 4,905,000
Grant date fair value of shares vested	$ 12.24	$ 11.12	$ 19.17	$ 12.60
Share-Based Compensation (Textuals)
Share-based compensation	1,000,000	400,000	2,000,000	800,000
Shortfall in tax benefit			0	0
Net cash proceed from excise of stock options			1,000,000	800,000
Actual income tax benefit from excise of stock options			1,100,000	200,000
Look back period to estimate expected volatility of stock option grants			5.5	5.5
Intrinsic value of outstanding stock option	11,300,000		11,300,000
Intrinsic value of exercisable stock option	7,200,000		7,200,000
Intrinsic value of exercised stock option			4,100,000
Remaining contract life of outstanding stock option	6.2		6.2
Remaining contract life of exercisable stock option	4.7		4.7
General and Administrative Expense [Member]
Employee Service Share Based Compensation Allocation of Recognized Period Costs (Textuals)
Share-based compensation expenses	3,100,000	2,300,000	5,600,000	4,400,000
Operating Lease Expense [Member]
Employee Service Share Based Compensation Allocation of Recognized Period Costs (Textuals)
Share-based compensation expenses	100,000	100,000	200,000	200,000
Employee Stock Option [Member]
Employee Service Share Based Compensation Allocation of Recognized Period Costs (Textuals)
Unrecognized compensation cost related to stock options	5,100,000		5,100,000
Weighted average recognition period of cost related to stock options			1.1
Restricted Stock [Member]
Employee Service Share Based Compensation Allocation of Recognized Period Costs (Textuals)
Unrecognized compensation cost related to stock options	$ 19,800,000		$ 19,800,000
Weighted average recognition period of cost related to stock options			1.4
Grant date fair value of shares vested			$ 8.1

Employee Service Share Based Compensation Allocation Of Recognized Period Costs.

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Look back period to estimate expected volatility of stock option grants.

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Remaining contract life of exercisable stock option.

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Share Based Compensation Textuals Abstract.

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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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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 component of income tax expense representing amounts paid or payable (or refundable) which are classified as "income taxes" as determined by applying the provisions of enacted tax law to other than the taxable Income or Loss from continuing operations for the period. Items affecting income taxes and required to be disclosed, but not included elsewhere, would also be designated as "Other".

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The cash inflow associated with the amount received from holders exercising their stock options. This item inherently excludes any excess tax benefit, which the entity may have realized and reported separately.

+ References

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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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The total dollar difference between fair values of the underlying shares reserved for issuance and exercise prices of vested portions of options outstanding and currently exercisable under the option plan as of the balance sheet date.

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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.

+ References

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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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The total dollar difference between fair values of the underlying shares reserved for issuance and exercise prices pertaining to options outstanding under the plan as of the balance sheet date.

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The weighted average remaining life of the exercisable stock options as of the balance sheet date for all option plans in the customized range of exercise prices.

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Reductions in the entity's income taxes that arise when compensation cost (from non-qualified stock options) recognized on the entity's tax return exceeds compensation cost from non-qualified stock options recognized on the income statement. This element increases net cash provided by operating activities.

+ References

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