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Comprehensive Income - Schedule of Changes in Balances of Each Component of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Restated					$ (55,139)
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets					(2,900)
Changes In Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	$ 19,088	$ 45,854	$ (48,715)	$ (52,239)
Other comprehensive income before reclassifications	(26,144)	(81,869)	(147,336)	(233,956)
Amounts reclassified from accumulated other comprehensive income	(18,825)	(29,898)	(72,214)	(80,992)
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification				0
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	7,319	51,971	75,122	152,964
Ending Balance	26,407	97,825	26,407	97,825
Income Tax Expense (Benefit)	2,939	2,211	33,252	6,811
Unrealized Gains (Losses) on Available-for-Sale Securities [Member]
Changes In Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	157,304	153,634	85,903	30,755
Other comprehensive income before reclassifications	(49,714)	(90,742)	(174,179)	(264,318)
Amounts reclassified from accumulated other comprehensive income	(18,429)	(29,935)	(71,493)	(80,632)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	31,285	60,807	102,686	183,686
Ending Balance	188,589	214,441	188,589	214,441
Accumulated Translation Adjustment [Member]
Changes In Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	(145,489)	(114,567)	(141,527)	(93,634)
Other comprehensive income before reclassifications	23,570	8,873	27,532	29,806
Amounts reclassified from accumulated other comprehensive income	0	0	0	0
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(23,570)	(8,873)	(27,532)	(29,806)
Ending Balance	(169,059)	(123,440)	(169,059)	(123,440)
Accumulated Gain (Loss), Financial Liability, Fair Value Option, Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets					$ (2,900)
Changes In Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	(1,646)	(2,692)	(1,965)	(2,900)
Other comprehensive income before reclassifications	0	0	0	0
Amounts reclassified from accumulated other comprehensive income	(74)	340	245	548
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(74)	340	245	548
Ending Balance	(1,720)	(2,352)	(1,720)	(2,352)
Other Postretirement Benefits Plan [Member]
Changes In Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	8,919	9,479	8,874	10,640
Other comprehensive income before reclassifications	0	0	(689)	556
Amounts reclassified from accumulated other comprehensive income	(322)	(303)	(966)	(908)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(322)	(303)	(277)	(1,464)
Ending Balance	8,597	9,176	8,597	9,176
Reclassification out of Accumulated Other Comprehensive Income [Member] | Unrealized Gains (Losses) on Available-for-Sale Securities [Member]
Changes In Accumulated Other Comprehensive Income [Roll Forward]
Income Tax Expense (Benefit)	1,455	625	5,967	1,211
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Gain (Loss), Financial Liability, Fair Value Option, Attributable to Parent [Member]
Changes In Accumulated Other Comprehensive Income [Roll Forward]
Income Tax Expense (Benefit)			(50)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Other Postretirement Benefits Plan [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, before Tax	(241)	(241)	(722)	(723)
Changes In Accumulated Other Comprehensive Income [Roll Forward]
Amounts reclassified from accumulated other comprehensive income	(322)	(303)	(966)	(908)
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax	81	62	244	185
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	(322)	(303)	(966)	(908)
Income Tax Expense (Benefit)	$ 0	$ 0	$ 0	$ 0

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Accumulated change in equity from transactions and other events and circumstances from non-owner sources, net of tax effect, at period end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, unrealized gains and losses on certain investments in debt and equity securities, other than temporary impairment (OTTI) losses related to factors other than credit losses on available-for-sale and held-to-maturity debt securities that an entity does not intend to sell and it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis, as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge.

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