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Investments - Additional Information (Detail) (USD $) | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2013 Securities | Sep. 30, 2012 | Sep. 30, 2013 Securities | Sep. 30, 2012 | Dec. 31, 2012 Securities
Investment [Line Items] |  |  |  |  |
Other investments | $ 10,271,000 |  | $ 10,271,000 |  |
Number of securities accounted for gross unrealized losses | 158 |  | 158 |  | 49
Cost basis of securities at disposal | 1,700,000 | 11,100,000 | 6,700,000 | 31,200,000 |
Realized gains on sale of equity securities |  | 900,000 | 200,000 | 2,700,000 |
Realized loss on sale of equity securities | 500,000 |  |  |  |
Impairment losses recognized |  |  |  | 0 |
Equity Securities [Member] |  |  |  |  |
Investment [Line Items] |  |  |  |  |
Impairment losses recognized |  |  | $ 2,200,000 |  |

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- Definition For any sales of securities categorized as available-for-sale, this item represents the carrying amount of the sold security. + References No definition available. + Details
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- Definition This item represents the difference between the gross realized gains and losses realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26805-111562 + Details
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- Definition This item represents the gross loss realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities and excluding other than temporary impairments (OTTI), if any, recognized elsewhere. + References No definition available. + Details
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- Definition The amount by which the fair value of an investment is less than the amortized cost basis or carrying amount of that investment at the balance sheet date and the decline in fair value is deemed to be other than temporary, before considering whether or not such amount is recognized in earnings or other comprehensive income. + 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 (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 35 -Paragraph 34 -URI http://asc.fasb.org/extlink&oid=27723805&loc=d3e25351-111560 + Details
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- Definition Other investments not otherwise specified in the taxonomy. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.12) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 12 -Article 5 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 1 -Subparagraph g -Article 7 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.1(f,g)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 + Details
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