Note 5 - Share-based Compensation (Details Textual) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized	2.3
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	4 years 200 days
The 2001 Equity Incentive Plan [Member] \| Common Class A [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized	1,800,000
The 2001 Equity Incentive Plan [Member] \| Common Class B [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized	300,000
The 2001 Equity Incentive Plan [Member] \| Minimum [Member] \| Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	1 year
Share-based Compensation Arrangement by Share-based Payment Award Option Term	5 years
The 2001 Equity Incentive Plan [Member] \| Maximum [Member] \| Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	5 years
Share-based Compensation Arrangement by Share-based Payment Award Option Term	10 years
Director Plan 2004 [Member] \| Common Class A [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized	1,650,000
Common Stock Options Granted to Directors	36,000
Director Plan 2004 [Member] \| Common Class B [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized	275,000
Common Stock Options Granted to Directors	6,000
Director Plan 2004 [Member] \| Normal Term [Member]
Share-based Compensation Arrangement by Share-based Payment Award Option Term	10 years
Director Plan 2004 [Member] \| Termination of Service [Member]
Share-based Compensation Arrangement by Share-based Payment Award Option Term	3 years
Director Plan 2004 [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	1 year
The 2006 Equity Incentive Plan [Member] \| Common Class A [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized	1,800,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	81,306	24,166
The 2006 Equity Incentive Plan [Member] \| Common Class B [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized	300,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	13,551	2,217
The 2006 Equity Incentive Plan [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award Option Term	5 years
The 2006 Equity Incentive Plan [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award Option Term	10 years
Common Class A [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	81,306
Common Class B [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	13,551

Number of options awarded to directors on date of annual meeting upon reelection or retention.

No definition available.

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Balance Type:	na
Period Type:	instant

- Definition

Reflects the number of years from grant to when the share-based award expires as specified in the award agreement.

+ References

No definition available.

+ Details

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- Definition

Unrecognized cost of unvested share-based compensation awards.

+ 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 (i)

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

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- Definition

Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

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- Definition

Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ 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 (a)(1)

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

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- Definition

The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

+ 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 (a)(3)

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

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- Definition

Gross number of share options (or share units) granted during the period.

+ References

No definition available.

+ Details

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