Marketable Securities and Fair Value Measurements Additional Information (Details) (USD $) In Thousands, unless otherwise specified	1 Months Ended	3 Months Ended	6 Months Ended	12 Months Ended
Mar. 31, 2013	Jun. 30, 2013	Mar. 31, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Investments, Debt and Equity Securities [Abstract]
Asset Impairment Charges	$ 26,300	$ 0	$ 26,300	$ 0	$ 26,320	$ 0
Impairment of goodwill		$ 0	$ 40,700	$ 0	$ 40,693	$ 0
Maturity Period Used To Classify Investments							2 years
Marketable Securities, Weighted Average Remaining Maturity					10 months		10 months

The charge against earnings resulting from the aggregate write down of all assets from their carrying value to their fair value.

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Loss recognized during the period that results from the write-down of goodwill after comparing the implied fair value of reporting unit goodwill with the carrying amount of that goodwill. Goodwill is assessed at least annually for impairment.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

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