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Stock-Based Compensation (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Components of stock-based compensation expense
Total stock-based compensation	$ 5,205	$ 2,154
Stock options [Member]
Components of stock-based compensation expense
Total stock-based compensation	962	946
Restricted stock awards [Member]
Components of stock-based compensation expense
Total stock-based compensation	3,182	1,208
Performance based restricted stock units [Member]
Components of stock-based compensation expense
Total stock-based compensation	$ 1,061	$ 0

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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