Short-Term and Long-Term Investments - Rollforward of Credit (Gain) Loss Recognized in Earnings on Available-for-Sale Auction Rate Securities (Detail) - USD ($) $ in Thousands	6 Months Ended
Jun. 30, 2015	Jun. 30, 2014
Available-for-sale Securities, Debt Maturities [Abstract]
Balance at the beginning of the period	$ 84	$ 395
Changes in the amount related to credit gain for which other-than- temporary impairment was not previously recognized	(8)	(20)
Balance at the end of the period	$ 76	$ 375

The cumulative amount of credit losses recognized in earnings related to debt securities held for which a portion of an other than temporary impairment (OTTI) was recognized in other comprehensive income (a component of shareholders' equity).

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 8

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27340-111563

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