Note 10 - 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, 2015	Mar. 31, 2014
Numerator:
Income from continuing operations applicable to common stockholders	$ 40,653	$ 24,694
Denominator:
Weighted average number of shares outstanding used to calculate basic income per share (in Shares)	26,283	25,973
Weighted average number of shares outstanding used to calculate diluted income per share from continuing operations (in Shares)	26,519	26,320
Basic income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ 1.55	$ 0.95
Diluted income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ 1.53us-gaap_EarningsPerShareDiluted	$ 0.94us-gaap_EarningsPerShareDiluted
Common Class A [Member] \| Equity Option [Member]
Antidilutive Securities
Shares issuable pursuant to stock options not included since they were antidilutive (in Shares)	15	16
Common Class A [Member] \| Distributed [Member]
Numerator:
Reallocation of income as a result of conversion of dilutive stock options	4	4
Reallocation of income due to conversion of Class B to Class A shares	407	329
Common Class A [Member] \| Diluted [Member]
Numerator:
Distributed income applicable to common stockholders	(4,216)	(3,378)
Numerator:
Income applicable to common stockholders	4,216	3,378
Income from continuing operations applicable to common stockholders	36,437	21,316
Common Class A [Member] \| Undistributed [Member]
Numerator:
Reallocation of income as a result of conversion of dilutive stock options	32	28
Reallocation of income due to conversion of Class B to Class A shares	3,520	2,075
Common Class A [Member]
Numerator:
Income from continuing operations applicable to common stockholders	36,690	22,258
Distributed income applicable to common stockholders	(3,805)	(3,045)
Basic undistributed income from continuing operations applicable to common stockholders	32,885	19,213
Denominator:
Weighted average number of shares outstanding used to calculate basic income per share (in Shares)	23,721	23,411
Weighted average number of shares from stock options (in Shares)	236	347
Conversion of Class B to Class A common shares outstanding (in Shares)	2,562	2,562
Weighted average number of shares outstanding used to calculate diluted income per share from continuing operations (in Shares)	26,519	26,320
Basic income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ 1.55	$ 0.95
Basic distributed income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ (0.16)	$ (0.13)
Basic undistributed income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ 1.39	$ 0.82
Diluted income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ 1.53	$ 0.94
Diluted distributed income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ (0.16)	$ (0.13)
Diluted undistributed income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ 1.37	$ 0.81
Numerator:
Income applicable to common stockholders	3,805	3,045
Income from continuing operations applicable to common stockholders	32,885	19,213
Common Class B [Member] \| Distributed [Member]
Numerator:
Reallocation of income as a result of conversion of dilutive stock options	(4)	(4)
Common Class B [Member] \| Diluted [Member]
Numerator:
Distributed income applicable to common stockholders	(407)	(329)
Numerator:
Income applicable to common stockholders	407	329
Income from continuing operations applicable to common stockholders	3,520	2,075
Common Class B [Member] \| Undistributed [Member]
Numerator:
Reallocation of income as a result of conversion of dilutive stock options	(32)	(28)
Common Class B [Member]
Numerator:
Income from continuing operations applicable to common stockholders	3,963	2,436
Distributed income applicable to common stockholders	(411)	(333)
Basic undistributed income from continuing operations applicable to common stockholders	3,552	2,103
Denominator:
Weighted average number of shares outstanding used to calculate basic income per share (in Shares)	2,562	2,562
Weighted average number of shares outstanding used to calculate diluted income per share from continuing operations (in Shares)	2,562	2,562
Basic income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ 1.55	$ 0.95
Basic distributed income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ (0.16)	$ (0.13)
Basic undistributed income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ 1.39	$ 0.82
Diluted income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ 1.53	$ 0.94
Diluted distributed income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ (0.16)	$ (0.13)
Diluted undistributed income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ 1.37	$ 0.81
Numerator:
Income applicable to common stockholders	411	333
Income from continuing operations applicable to common stockholders	$ 3,552	$ 2,103

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Amount of increase (decrease) to net income used for calculating diluted earnings per share (EPS), resulting from the assumed exercise of stock options or restrictive stock units (RSUs).

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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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Amount of increase (decrease) to net income used for calculating diluted earnings per share (EPS), resulting from the assumed exercise of dilutive convertible securities excluding adjustments related to ESOP convertible preferred stock, stock options, and restrictive stock units.

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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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The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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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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