Investment in short-term money-market instruments (such as commercial paper, banker's acceptances, repurchase agreements, government securities, certificates of deposit, and so forth) which are highly liquid (that is, readily convertible to known amounts of cash) and so near their maturity that they present an insignificant risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify as cash equivalents by definition. Original maturity means an 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.

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Cash Equivalents

-URI http://asc.fasb.org/extlink&oid=6507016

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

Available-For-Sale Securities (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2013 Asset-backed securities and collateralized mortgage obligations	Dec. 31, 2012 Asset-backed securities and collateralized mortgage obligations	Dec. 31, 2013 Maximum Commercial paper	Dec. 31, 2012 Maximum Commercial paper	Dec. 31, 2013 Maximum Asset-backed securities and collateralized mortgage obligations	Dec. 31, 2012 Maximum Asset-backed securities and collateralized mortgage obligations	Dec. 31, 2013 Maximum Corporate notes and bonds	Dec. 31, 2012 Maximum Corporate notes and bonds
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, maturities				1 year	1 year	26 years	26 years	3 years	3 years
Commercial paper secured by mortgaged-backed securities		$ 5.6	$ 6.3
Asset-backed and mortgage-backed securities impairment	$ 1.6