Separation And Distribution Of Prothena Business (Summary Of Assets Transferred To Prothena) (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012
Business Acquisition [Line Items]
Total value of the Prothena distribution	$ 105.7
Prothena [Member]
Business Acquisition [Line Items]
Cash and cash equivalents	125.0
Net assets	3.2
Total assets transferred	128.2
Fair value of operating lease guarantee	0.4
Less: Initial carrying value of available for sale interest in Prothena	(22.9)
Total value of the Prothena distribution	$ 105.7

- Definition

For the disposal group, including a component of the entity (discontinued operation), cash includes currency on hand as well as demand deposits with banks or financial institutions. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid investments that are both readily convertible to known amounts of cash, and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months.

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