Note 6 - Stock-based Compensation (Details) - Summary of Restricted Common Stock Activity (Restricted Stock [Member], USD $)	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Note 6 - Stock-based Compensation (Details) - Summary of Restricted Common Stock Activity [Line Items]
Number of Shares, Beginning of Period	385,056	274,838
Weighted- Average Grant Date Fair Value Per Share, Beginning of Period	$ 9.09	$ 4.43
Number of Shares, Granted	150,308	312,961
Weighted- Average Grant Date Fair Value Per Share, Granted	$ 10.27	$ 11.78
Number of Shares, Vested	(197,858)	(202,743)
Weighted- Average Grant Date Fair Value Per Share, Vested	$ 9.16	$ 6.93
Number of Shares, End of Period	337,506	385,056
Weighted- Average Grant Date Fair Value Per Share, End of Period	$ 9.57	$ 9.09
Common Class A [Member]
Note 6 - Stock-based Compensation (Details) - Summary of Restricted Common Stock Activity [Line Items]
Number of Shares, Beginning of Period	204,473	0
Weighted- Average Grant Date Fair Value Per Share, Beginning of Period	$ 9.81	$ 0
Number of Shares, Granted	287,513	236,294
Weighted- Average Grant Date Fair Value Per Share, Granted	$ 9.37	$ 9.80
Number of Shares, Vested	(117,293)	(31,821)
Weighted- Average Grant Date Fair Value Per Share, Vested	$ 9.85	$ 9.75
Number of Shares, End of Period	374,693	204,473
Weighted- Average Grant Date Fair Value Per Share, End of Period	$ 9.46	$ 9.81

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)(iii)(1)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

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- Definition

The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)(i)-(ii)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)(i)-(ii)

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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)(iii)(2)

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The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)(iii)(2)

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