Earnings per Share - Computation of Basic and Diluted Earnings per Share (EPS) (Parenthetical) (Detail) - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2014	Mar. 31, 2014
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Change in net income for purposes of computing diluted earnings per share	$ 3
Convertible Senior Notes, 7.25, Due in 2014 [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Debt instrument, stated interest rate percentage	7.25%	7.25%

Contractual interest rate for funds borrowed, under the debt agreement.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22(a)(1))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant