Stock-Based Compensation - Activity for Stock Option (Parenthetical) (Detail) (Stock Options [Member], USD $) In Millions, except Per Share data, unless otherwise specified	Dec. 31, 2014
Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock options expected to vest, shares	0.7
Stock options expected to vest, weighted-average exercise price	$ 11.27

The number of exercisable share options (fully vested and expected to vest) that may be converted as of the balance sheet date.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (e)(2)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableNumber
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant