Stock-Based Compensation (Details 3) (USD $)	3 Months Ended
Mar. 31, 2012 Y	Mar. 31, 2011 Y
Stock options
Weighted-average assumptions
Risk-free interest rate, minimum (as a percent)	1.00%	2.38%
Risk-free interest rate, maximum (as a percent)	1.17%	2.46%
Expected life (in years)	6	6
Volatility (as a percent)	0.55%	0.49%
Weighted-average estimated fair value of stock options granted (in dollars per share)	$ 9.88	$ 10.86
Stockholders' equity (net capital deficiency):
Shares exercised	247,818
Shares exercised, Weighted-Average Exercise Price of Outstanding Options (in dollars per share)	$ 8.13
Total cash proceed	$ 2,015,000
Stock options \| 2004 Equity Incentive Plan
Compensation Awards
Number of Compensation Awards Granted (in shares)	118,000	94,000
Weighted-Average Exercise Price (in dollars per share)	$ 19.05	$ 22.12
RSUs \| 2004 Equity Incentive Plan \| Time-Based
Compensation Awards
Number of Compensation Awards Granted (in shares)	468,541	394,580
Weighted-Average Fair Value (in dollars per share)	$ 18.12	$ 24.59
RSAs \| 2004 Equity Incentive Plan \| Time-Based
Compensation Awards
Number of Compensation Awards Granted (in shares)	402,500	1,148,000
Weighted-Average Fair Value (in dollars per share)	$ 18.11	$ 24.70
RSAs \| 2004 Equity Incentive Plan \| Performance-Contingent
Compensation Awards
Number of Compensation Awards Granted (in shares)	44,500	1,290,000
Weighted-Average Fair Value (in dollars per share)	$ 18.11	$ 24.73

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.

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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 period of time an equity-based award is expected to be outstanding. An equity-based award's expected term is generally determined based on, among other factors, the instrument's contractual term and the effects of employees' expected exercise and post-vesting employment termination behavior.

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The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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The maximum risk-free interest rate assumption that is used in valuing an option on its own shares.

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The minimum risk-free interest rate assumption that is used in valuing an option on its own shares.

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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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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 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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Number of share options (or share units) exercised during the current period.

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