Marketable Securities and Fair Value Measurements Additional Information (Details) (USD $) In Thousands, unless otherwise specified	1 Months Ended	3 Months Ended			9 Months Ended		12 Months Ended
	Mar. 31, 2013	Sep. 30, 2013	Mar. 31, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 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	$ 24,665	$ 40,693	$ 24,665
Maturity Period Used To Classify Investments					2 years
Marketable Securities, Weighted Average Remaining Maturity					8 months		10 months