Investments - Additional Information (Detail) (USD $)	3 Months Ended	12 Months Ended
Dec. 31, 2013	Dec. 31, 2012	Sep. 30, 2013
Amortized Cost And Fair Value Debt Securities [Abstract]
Maturity of short-term investments	Less than one year		Less than one year
Maturity of long-term investments	Greater than one year		Greater than one year
Other-than-temporary impairment charges recognized	$ 0	$ 0

The amount of other than temporary impairment (OTTI) losses on equity securities, OTTI related to credit losses on debt securities, and OTTI losses on debt securities when the entity intends to sell the securities or it is more likely than not that the entity will be required to sell the securities before recovery of its amortized cost basis. Additionally, this item includes OTTI losses recognized during the period on investments accounted for under the cost method of accounting.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 8B

-URI http://asc.fasb.org/extlink&oid=27724398&loc=SL6284393-111563

Name:	us-gaap_OtherThanTemporaryImpairmentLossesInvestmentsPortionRecognizedInEarningsNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration