Research and development expenses: (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended
Dec. 31, 2011	Dec. 31, 2012	Mar. 31, 2011
Research and development expenses:
Research and development expenses	$ 37,178	$ 74,040	$ 25,602
Program funding	(604)	(842)	(982)
Research and development	$ 36,574	$ 73,198	$ 24,620

The amount of compensation earned (contract income) under a research and development arrangement accounted for as a contract to perform research and development for others.

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The aggregate costs incurred (1) in a planned search or critical investigation aimed at discovery of new knowledge with the hope that such knowledge will be useful in developing a new product or service, a new process or technique, or in bringing about a significant improvement to an existing product or process; or (2) to translate research findings or other knowledge into a plan or design for a new product or process or for a significant improvement to an existing product or process whether intended for sale or the entity's use, during the reporting period charged to research and development projects, including the costs of developing computer software up to the point in time of achieving technological feasibility, and costs allocated in accounting for a business combination to in-process projects deemed to have no alternative future use.

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