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Stock-Based Compensation - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified | 9 Months Ended | 3 Months Ended | 9 Months Ended | 3 Months Ended | 9 Months Ended |  | 9 Months Ended |
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Sep. 30, 2013 | Sep. 30, 2012 | Sep. 30, 2013 Restricted Stock [Member] | Sep. 30, 2012 Restricted Stock [Member] | Sep. 30, 2013 Restricted Stock [Member] | Sep. 30, 2012 Restricted Stock [Member] | Sep. 30, 2013 Restricted Stock [Member] Minimum [Member] | Sep. 30, 2013 Restricted Stock [Member] Maximum [Member] | Sep. 30, 2013 Performance Share Units [Member] | Sep. 30, 2012 Performance Share Units [Member] | Sep. 30, 2013 Performance Share Units [Member] | Sep. 30, 2012 Performance Share Units [Member] | Sep. 30, 2013 Performance Share Units [Member] Minimum [Member] | Sep. 30, 2013 Performance Share Units [Member] Maximum [Member] | Sep. 30, 2013 PSU 2013 Grants [Member] | Feb. 15, 2013 PSU 2013 Grants [Member] | Sep. 30, 2013 PSU 2012 Grants [Member] | Jul. 30, 2012 PSU 2012 Grants [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Award vesting period |  |  |  |  | 3 years |  |  |  |  |  |  |  |  |  |  |  |  |
Annual forfeiture rate |  |  |  |  |  |  | 0.00% | 11.00% |  |  | 2.70% |  |  |  |  |  |  |
Stock-based compensation expense | $ 8,411 | $ 6,627 | $ 2,600 | $ 2,600 | $ 7,100 | $ 6,500 |  |  | $ 500 | $ 200 | $ 1,300 | $ 200 |  |  |  |  |  |
Right to received shares of common stock |  |  |  |  |  |  |  |  | 1 |  | 1 |  |  |  |  |  |  |
Performance share units initial performance period, years |  |  |  |  |  |  |  |  |  |  | 3 years |  |  |  |  |  |  |
PSU granted percentage of earnings |  |  |  |  |  |  |  |  |  |  |  |  | 0.00% | 200.00% |  |  |  |
Amortized performance period |  |  |  |  |  |  |  |  |  |  | 4 years |  |  |  | 4 years |  | 4 years 2 days |
Number of trading days |  |  |  |  |  |  |  |  |  |  | 30 days |  |  |  |  |  |  |
Valuation model standard deviation term |  |  |  |  |  |  |  |  |  |  | 2 years |  |  |  |  |  |  |
Expected percentage earned |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 112.00% |  | 98.00%

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- Definition The aggregate amount of noncash, equity-based employee remuneration. This may include the value of stock or unit options, amortization of restricted stock or units, and adjustment for officers' compensation. As noncash, this element is an add back when calculating net cash generated by operating activities using the indirect method. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 + Details
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- Definition Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Expected term of share-based compensation awards, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 14.D.2) -URI http://asc.fasb.org/extlink&oid=27013229&loc=d3e301413-122809 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2)(i) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 14 -Section D -Subsection 2 + Details
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