Fair Value Measurements - Additional Information (Detail) (Auction Rate Securities [Member], USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2012
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Net proceeds from liquidation of auction rate security	$ 25.4
Loss on liquidation of the securities	3.2
Impairment on auction rate securities	0.9
Securities Redeemed at Less Than Par Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Par value of auction rate securities redeemed	29.5
Securities Redeemed at Par Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Par value of auction rate securities redeemed	$ 24.9

The amount by which the fair value of an investment is less than the amortized cost basis or carrying amount of that investment at the balance sheet date and the decline in fair value is deemed to be other than temporary, before considering whether or not such amount is recognized in earnings or other comprehensive income.

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- Definition

This item represents the total realized gain (loss) included in earnings for the period as a result of selling marketable securities categorized as trading, available-for-sale, or held-to-maturity. Additionally, this item would include any losses recognized for other than temporary impairments (OTTI) of the subject investments in debt and equity securities.

+ References+ Details

- Definition

The cash inflow associated with the aggregate amount received by the entity through sale or maturity of marketable securities (held-to-maturity or available-for-sale) during the period.

+ References

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