Carrying Value of Nonmarketable Securities (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Investments Debt and Equity Securities [Abstract]
Carrying value of nonmarketable equity securities	$ 2,159	$ 2,740
Common Stock
Investments Debt and Equity Securities [Abstract]
Carrying value of nonmarketable equity securities	1,359	1,940
Preferred Stock
Investments Debt and Equity Securities [Abstract]
Carrying value of nonmarketable equity securities	$ 800	$ 800

Includes other investments and securities that are not at fair value as of the balance sheet date and those that are not accounted for under the equity method.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.1)

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph a

-Subparagraph 1(g)

-Article 7

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