Schedule of Reported Available for Sale Marketable Securities (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	$ 488,532	$ 1,470,729
Available-for-sale marketable securities, Unrealized Gain	544	6,582
Available-for-sale marketable securities, Unrealized (Loss)	(3,369)	(3,406)
Available-for-sale marketable securities, Fair Market Value	485,707	1,473,905
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	461,349	1,350,896
Marketable securities
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	418,554	1,349,970
Available-for-sale marketable securities, Unrealized Gain	52	38
Available-for-sale marketable securities, Unrealized (Loss)	(196)	(2,029)
Available-for-sale marketable securities, Fair Market Value	418,410	1,347,979
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	405,959	1,288,844
Long-term marketable securities
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	69,978	120,759
Available-for-sale marketable securities, Unrealized Gain	492	6,544
Available-for-sale marketable securities, Unrealized (Loss)	(3,173)	(1,377)
Available-for-sale marketable securities, Fair Market Value	67,297	125,926
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	$ 55,390	$ 62,052

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

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

+ References

No definition available.

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This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References

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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.

+ References

No definition available.

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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.

+ References

No definition available.

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