v3.7.0.1

Investments - Components of Investments (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Cost Basis	$ 252,722	$ 305,915
Unrealized Gains	1	2
Unrealized Losses	(347)	(693)
Fair Value	252,376	305,224
Investment Type [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost Basis	250,160	303,521
Unrealized Gains	1	2
Unrealized Losses	(347)	(693)
Fair Value	249,814	302,830
Investment Type [Member] | Money Market Mutual Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost Basis	18,079	18,118
Fair Value	18,079	18,118
Investment Type [Member] | Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost Basis	17,008	27,906
Unrealized Losses	(10)	(39)
Fair Value	16,998	27,867
Investment Type [Member] | US Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost Basis	15,301	13,295
Unrealized Losses	(19)	(32)
Fair Value	15,282	13,263
Investment Type [Member] | Corporate Bonds and Notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost Basis	199,772	244,202
Unrealized Gains	1	2
Unrealized Losses	(318)	(622)
Fair Value	199,455	243,582
Deferred Compensation Plan Assets [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost Basis	2,562	2,394
Fair Value	$ 2,562	$ 2,394

X

- Definition

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

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
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+ References

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+ References

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