Cash Equivalents, Restricted Cash and Short-term and Long-term Investments Classified as Available-for-sale Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 36,551	$ 66,247
Gross Unrealized Gains		2
Gross Unrealized Losses	(2)	(1)
Estimated Fair Value	36,549	66,248
Money Market Funds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	10,156	28,927
Estimated Fair Value	10,156	28,927
Money Market Funds \| Restricted cash (money market funds)
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	19,593	33,919
Estimated Fair Value	19,593	33,919
U.S. Government Agency Securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	6,802
Gross Unrealized Losses	(2)
Estimated Fair Value	6,800
Municipal Bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		295
Gross Unrealized Gains		1
Estimated Fair Value		296
Corporate Notes
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		3,106
Gross Unrealized Gains		1
Gross Unrealized Losses		(1)
Estimated Fair Value		3,106
Cash Equivalents
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value	10,156	28,927
Short-Term Investments
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value	$ 6,800	$ 3,402

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=65884222&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
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-URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27232-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
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-URI http://asc.fasb.org/extlink&oid=66010992&loc=d3e26610-111562

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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://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
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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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
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