Stock Based Compensation Plans - Additional Information (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	9 Months Ended	3 Months Ended	9 Months Ended
Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012 Restricted Stock	Sep. 30, 2013 Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Repurchase of stock for tax withholding			336,000	51,079
Vesting of restricted shares			1,050,000	183,750
Minimum withholding tax on restricted stocks	$ 1,639	$ 24	$ 1,600

The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)(iii)(2)

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

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Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration