Line items represent reporting concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
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This item represents the gross profit realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities.

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This item represents the net total realized and unrealized gain (loss) included in earnings for the period as a result of selling or holding marketable securities categorized as trading, available-for-sale, or held-to-maturity, including the unrealized holding gain (loss) of held-to-maturity securities transferred to the trading security category and the cumulative unrealized gain (loss) which was included in other comprehensive income (a separate component of shareholders' equity) for available-for-sale securities transferred to trading securities during the period. Additionally, this item would include any gains (losses) realized during the period from the sale of investments accounted for under the cost method of accounting and losses recognized for other than temporary impairments (OTTI) of the subject investments.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section 50
-Paragraph 9
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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The net realized gain (loss) on investments sold during the period, not including gains (losses) on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity, which, for cash flow reporting, is a component of proceeds from investing activities.

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Amount of gain (loss) realized from securities classified as trading.

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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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Amount of unrealized holding gain (loss) recognized in the income statement for investments in debt and equity securities and other forms of securities that provide ownership interests classified as trading.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of investments, not including unrealized gains or losses on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity, held at each balance sheet date and included in earnings for the period.

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Investments - Components of Net Realized and Unrealized Gains (Losses) (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Investment [Line Items]
Total net realized gains on sale									$ 15,910	$ 23,939	$ 13,979
Total net unrealized gains (losses)									(57,162)	38,680	56,672
Net realized and unrealized gains (losses)	$ (57,893)	$ (15,130)	$ (11,249)	$ 43,020	$ 7,971	$ (18,336)	$ 38,411	$ 34,573	(41,252)	62,619	70,651
Fixed maturity investments
Investment [Line Items]
Gross realized gains on fixed maturity securities, available-for-sale									396	196	705
Gross realized (losses) on fixed maturity securities, available-for-sale securities									(130)	(138)	(214)
Net realized gains (losses) on trading securities									(4,240)	5,143	(2,425)
Net unrealized gains (losses) on trading securities									(53,193)	17,283	(26,384)
Equity Securities
Investment [Line Items]
Net realized gains (losses) on trading securities									19,884	18,738	15,913
Net unrealized gains (losses) on trading securities									(22,269)	(8,571)	12,593
Other Investments
Investment [Line Items]
Total net unrealized gains (losses)									$ 18,300	$ 29,968	$ 70,463