Investments - Net Realized and Unrealized Gains (Losses) (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Gain (Loss) on Investments [Line Items]
Total net realized gains on sale	$ 2,203	$ 7,093	$ 786	$ 19,782
Other investments	(5,305)	11,056	(9,270)	34,618
Total net unrealized gains (losses)	35,784	(18,342)	75,165	11,989
Net realized and unrealized gains (losses)	37,987	(11,249)	75,951	31,771
Proceeds from sales of available-for-sale securities	18,200	16,500	33,600	59,800
Fixed maturity investments
Gain (Loss) on Investments [Line Items]
Gross realized gains on fixed maturity securities, available-for-sale	114	39	379	153
Gross realized (losses) on fixed maturity securities, available-for-sale	(1)	(1)	(244)	(9)
Net realized gains (losses) on trading securities	1,535	1,886	(377)	3,752
Net unrealized gains (losses) on trading securities	40,472	(22,953)	82,212	(9,065)
Equity Securities
Gain (Loss) on Investments [Line Items]
Net realized gains (losses) on trading securities	555	5,169	1,028	15,886
Net unrealized gains (losses) on trading securities	$ 617	$ (6,445)	$ 2,223	$ (13,564)

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 gross loss 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
-Topic 320
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-Paragraph 9
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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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The aggregate net change in the difference between the fair value and the carrying value, or in the comparative fair values, of marketable securities categorized as trading held at each balance sheet date, that was included in earnings for the period, which may have arisen from (a) securities classified as trading, (b) the unrealized holding gain (loss) on held-to-maturity securities transferred to the trading security category, and (c) the cumulative unrealized gain (loss) which was included in other comprehensive income (a separate component of shareholders' equity) on available-for-sale securities transferred to trading securities during the period.

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The cash inflow associated with the sale of debt and equity securities classified as available-for-sale securities.

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Line items represent financial 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.

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No definition available.

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

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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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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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