Stock-Based Compensation (Details 4) (USD $)	3 Months Ended
Mar. 31, 2013
Long-Term Performance Based Plans
Restricted stock unit activity
Total restricted stock units outstanding, end of period (in shares)	2,117,580
Weighted - Average Grant Date Fair Value
Total restricted stock units outstanding, end of period (in dollars per share)	$ 28.93
Restricted stock units
Restricted stock unit activity
Total restricted stock units outstanding, beginning of period (in shares)	1,185,080
Granted (in shares)	937,500
Forfeited and cancelled (in shares)	(5,000)
Total restricted stock units outstanding, end of period (in shares)	2,117,580
Weighted - Average Grant Date Fair Value
Total restricted stock units outstanding, beginning of period (in dollars per share)	$ 22.99
Granted (in dollars per share)	$ 36.40
Forfeited and cancelled (in dollars per share)	$ 24.32
Total restricted stock units outstanding, end of period (in dollars per share)	$ 28.93

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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- Definition

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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