Fair Value of Financial Instruments (Details 2) (Auction rate securities, USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2012 Y
Quantitative information for Level 3 Fair Value Measurements Assets
Fair value Assets	17,729
Weighted Average \| Discounted cash flow
Quantitative information for Level 3 Fair Value Measurements Assets
Estimated yield (as a percent)	2.00%
Expected holding periods (in years)	10
Estimated discount rate (as a percent)	3.40%

This element represents the aggregate of the assets reported on the balance sheet at period end measured at fair value by the entity. This element is intended to be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements.

No definition available.

Name:	us-gaap_AssetsFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant