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Schedule of Reported Available for Sale Marketable Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	$ 259,011	$ 1,470,729
Available-for-sale marketable securities, Unrealized Gain	592	6,582
Available-for-sale marketable securities, Unrealized (Loss)	(2,967)	(3,406)
Available-for-sale marketable securities, Fair Market Value	256,636	1,473,905
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	191,978	1,350,896
Marketable securities
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	190,100	1,349,970
Available-for-sale marketable securities, Unrealized Gain	88	38
Available-for-sale marketable securities, Unrealized (Loss)	(92)	(2,029)
Available-for-sale marketable securities, Fair Market Value	190,096	1,347,979
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	140,262	1,288,844
Long-term marketable securities
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	68,911	120,759
Available-for-sale marketable securities, Unrealized Gain	504	6,544
Available-for-sale marketable securities, Unrealized (Loss)	(2,875)	(1,377)
Available-for-sale marketable securities, Fair Market Value	66,540	125,926
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	$ 51,716	$ 62,052

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- Definition

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

+ References

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- Definition

Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

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- Definition

Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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This item represents the aggregate fair value of investments in debt and equity securities in an unrealized loss position which are categorized neither as held-to-maturity nor trading securities.

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