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Stock-Based Compensation Expense Components (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Compensation Related Costs Disclosure [Line Items]
Stock-based compensation expense	$ 4,005	$ 3,990
Stock options
Compensation Related Costs Disclosure [Line Items]
Stock-based compensation expense	3,255	3,111
Restricted stock units and awards
Compensation Related Costs Disclosure [Line Items]
Stock-based compensation expense	690	422
Performance-based restricted stock units
Compensation Related Costs Disclosure [Line Items]
Stock-based compensation expense	35	338
ESPP
Compensation Related Costs Disclosure [Line Items]
Stock-based compensation expense	$ 25	$ 119

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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