Investments - Summary of Available-for-Sale Investments at Fair Value (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities
Cost	$ 11,569	$ 28,364
Gross Unrealized (Losses)	(2)	(17)
Gross Unrealized Gains	1
Estimated Fair Value	11,568	28,347
Estimated Fair Value - Short-term investments	11,568	28,347
Short-term investments
Schedule of Available-for-sale Securities
Cost	11,569	28,364
Gross Unrealized (Losses)	(2)	(17)
Gross Unrealized Gains	1
Estimated Fair Value - Short-term investments	11,568	28,347
Short-term investments \| Corporate bonds
Schedule of Available-for-sale Securities
Cost	4,477	19,740
Gross Unrealized (Losses)	(1)	(11)
Estimated Fair Value - Short-term investments	4,476	19,729
Short-term investments \| Municipal bonds
Schedule of Available-for-sale Securities
Cost	7,092	8,624
Gross Unrealized (Losses)	(1)	(6)
Gross Unrealized Gains	1
Estimated Fair Value - Short-term investments	$ 7,092	$ 8,618

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
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-Section 50
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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
-Paragraph 1
-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.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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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
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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
-Subparagraph (SX 210.5-02.2)
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Amount of investment in debt and equity securities categorized neither as trading securities nor held-to-maturity securities and intended be sold or mature one year or operating cycle, if longer.

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