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Comprehensive Income - Schedule of Changes in Balances of Each Component of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
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	$ (52,239)	(38,990)
Other comprehensive income before reclassifications	(87,454)	20,114
Amounts reclassified from accumulated other comprehensive income	(81,030)	13,453
Income Tax Expense (Benefit)	(5,134)	(44,464)	$ (30,709)
Net current period other comprehensive income	6,424	(13,249)
Ending Balance	(48,715)	(52,239)	(38,990)
Unrealized Gains (Losses) on Available-for-Sale Securities [Member]
Changes In Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	30,755	118,863
Other comprehensive income before reclassifications	(135,903)	96,325
Amounts reclassified from accumulated other comprehensive income	(80,755)	14,805
Net current period other comprehensive income	55,148	(88,108)
Ending Balance	85,903	30,755	118,863
Accumulated Translation Adjustment [Member]
Changes In Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	(93,634)	(167,220)
Other comprehensive income before reclassifications	47,893	(73,586)
Amounts reclassified from accumulated other comprehensive income	0	0
Net current period other comprehensive income	(47,893)	73,586
Ending Balance	(141,527)	(93,634)	(167,220)
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	(2,900)
Other comprehensive income before reclassifications	0
Amounts reclassified from accumulated other comprehensive income	935
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	935
Ending Balance	(1,965)	(2,900)
Other Postretirement Benefits Plan [Member]
Changes In Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	10,640	9,367
Other comprehensive income before reclassifications	556	(2,625)
Amounts reclassified from accumulated other comprehensive income	(1,210)	(1,352)
Net current period other comprehensive income	(1,766)	1,273
Ending Balance	$ 8,874	10,640	$ 9,367
Accounting Standards Update 2016-09 [Member] | Retained Earnings [Member]
Changes In Accumulated Other Comprehensive Income [Roll Forward]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification		$ (6,588)

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Accumulated Other Comprehensive Income (Loss), Restated

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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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