Note 12 - Net Income Per Share of Class A and Class B Common Stock (Details) - Earnings Per Share Reconciliation (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
Mar. 31, 2014	Mar. 31, 2013
Numerator:
Income from continuing operations applicable to common stockholders	$ 24,694	$ 21,882
Denominator:
Weighted average number of shares outstanding used to calculate basic income per share (in Shares)	25,973	25,626
Weighted average number of shares outstanding used to calculate diluted income per share from continuing operations (in Shares)	26,320	26,054
Diluted income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ 0.94	$ 0.84
Basic income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ 0.95	$ 0.85
Equity Option [Member] \| Common Class A [Member]
Antidilutive Securities
Shares issuable pursuant to stock options not included since they were antidilutive (in Shares)	16	20
Common Class A [Member] \| Basic [Member]
Numerator:
Distributed income applicable to common stockholders	(3,045)
Numerator:
Distributed income applicable to common stockholders	3,045
Common Class A [Member] \| Distributed [Member]
Numerator:
Reallocation of income as a result of conversion of dilutive stock options	4
Reallocation of income due to conversion of Class B to Class A	329
Common Class A [Member] \| Diluted [Member]
Numerator:
Distributed income applicable to common stockholders	(3,378)
Numerator:
Distributed income applicable to common stockholders	3,378
Common Class A [Member] \| Undistributed [Member]
Numerator:
Reallocation of income as a result of conversion of dilutive stock options	28	39
Reallocation of income due to conversion of Class B to Class A	2,075	2,318
Common Class A [Member]
Numerator:
Income from continuing operations applicable to common stockholders	22,258	19,525
Undistributed income from continuing operations applicable to common stockholders	19,213	19,525
Denominator:
Weighted average number of shares outstanding used to calculate basic income per share (in Shares)	23,411	22,866
Weighted average number of shares from stock options (in Shares)	347	428
Conversion of Class B to Class A common shares outstanding (in Shares)	2,562	2,760
Weighted average number of shares outstanding used to calculate diluted income per share from continuing operations (in Shares)	26,320	26,054
Diluted income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ 0.94	$ 0.84
Diluted distributed income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ (0.13)
Diluted undistributed income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ 0.81	$ 0.84
Basic income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ 0.95	$ 0.85
Basic distributed income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ (0.13)
Basic undistributed income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ 0.82	$ 0.85
Numerator:
Diluted undistributed income from continuing operations applicable to common stockholders	21,316	21,882
Common Class B [Member] \| Basic [Member]
Numerator:
Distributed income applicable to common stockholders	(333)
Numerator:
Distributed income applicable to common stockholders	333
Common Class B [Member] \| Distributed [Member]
Numerator:
Reallocation of income as a result of conversion of dilutive stock options	(4)
Common Class B [Member] \| Diluted [Member]
Numerator:
Distributed income applicable to common stockholders	(329)
Numerator:
Distributed income applicable to common stockholders	329
Common Class B [Member] \| Undistributed [Member]
Numerator:
Reallocation of income as a result of conversion of dilutive stock options	(28)	(39)
Common Class B [Member]
Numerator:
Income from continuing operations applicable to common stockholders	2,436	2,357
Undistributed income from continuing operations applicable to common stockholders	2,103	2,357
Denominator:
Weighted average number of shares outstanding used to calculate basic income per share (in Shares)	2,562	2,760
Weighted average number of shares outstanding used to calculate diluted income per share from continuing operations (in Shares)	2,562	2,760
Diluted income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ 0.94	$ 0.84
Diluted distributed income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ (0.13)
Diluted undistributed income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ 0.81	$ 0.84
Basic income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ 0.95	$ 0.85
Basic distributed income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ (0.13)
Basic undistributed income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ 0.82	$ 0.85
Numerator:
Diluted undistributed income from continuing operations applicable to common stockholders	$ 2,075	$ 2,318

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Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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The total amount of dividends declared in the period for each class of stock and the contractual amount of dividends (or interest on participating income bonds) that must be paid for the period (for example, unpaid cumulative dividends). Dividends declared in the current period do not include dividends declared in respect of prior-period unpaid cumulative dividends. Preferred dividends that are cumulative only if earned are deducted only to the extent that they are earned.

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Dividends declared in the period and the contractual amount of dividends (or interest on participating income bonds) that must be paid per security.

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The earnings attributable to each security on the basis that all of the earnings for the period had been distributed (to the extent that each security may share in earnings). This is the earnings amount which reflects the participation rights in undistributed earnings of each security.

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Amount of income (loss) from continuing operations attributable to the parent. Also defined as revenue less expenses and taxes from ongoing operations before extraordinary items but after deduction of those portions of income or loss from continuing operations that are allocable to noncontrolling interests.

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The amount of net income (loss) from continuing operations per each share of common stock or unit outstanding during the reporting period.

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Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of contingently issuable shares. Contingently issuable shares are those shares that are issuable for little or no cash contingent on certain conditions being met.

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Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of share based payment arrangements using the treasury stock method.

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The earnings that is allocated to common stock and participating securities to the extent that each security may share in earnings as if all of the earnings for the period had been distributed.

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The earnings that is allocated to common stock and participating securities to the extent that each security may share in earnings as if all of the earnings for the period had been distributed. Includes the adjustments resulting from the assumption that dilutive securities were converted, options or warrants were exercised, or that other shares were issued upon the satisfaction of certain conditions.

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The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period.

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