Stock Based Compensation - Unvested Stock Option Activity (Parenthetical) (Detail) (CEO And COO Performance Options [Member])	12 Months Ended
Dec. 31, 2012
CEO And COO Performance Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted, shares	1,000,000

Gross number of share options (or share units) granted during the period.

No definition available.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration