Fair Value Measurements - Additional Information (Detail) (Significant Unobservable Inputs (Level 3) [Member])	9 Months Ended	12 Months Ended
Sep. 30, 2013	Dec. 31, 2012
Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Discount rate of Senior Notes	10.41%	10.48%

Interest rate used to find the present value of an amount to be paid or received in the future as an input to measure fair value. For example, but not limited to, weighted average cost of capital (WACC), cost of capital, cost of equity and cost of debt.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (bbb)

-URI http://asc.fasb.org/extlink&oid=25499696&loc=d3e19207-110258

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