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		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Numerator:
Income from continuing operations applicable to common stockholders	$ 30,891	$ 23,092	$ 78,054	$ 59,731
Denominator:
Weighted average number of shares outstanding used to calculate basic income per share (in Shares)	25,866	25,469	25,776	25,730
Weighted average number of shares outstanding used to calculate diluted income per share from continuing operations (in Shares)	26,237	25,947	26,159	26,203
Diluted income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ 1.18	$ 0.89	$ 2.98	$ 2.28
Basic income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ 1.19	$ 0.91	$ 3.03	$ 2.32
Equity Option [Member] | Common Class A [Member]
Antidilutive Securities
Shares issuable pursuant to stock options not included since they were antidilutive (in Shares)	14		17	90
Common Class A [Member] | Basic [Member]
Numerator:
Distributed income applicable to common stockholders	(3,030)	(2,212)	(6,031)	(5,989)
Numerator:
Distributed income applicable to common stockholders	3,030	2,212	6,031	5,989
Common Class A [Member] | Distributed [Member]
Numerator:
Reallocation of income as a result of conversion of dilutive stock options	5	6	10	17
Reallocation of income due to conversion of Class B to Class A	328	327	678	937
Common Class A [Member] | Diluted [Member]
Numerator:
Distributed income applicable to common stockholders	(3,363)	(2,545)	(6,719)	(6,943)
Numerator:
Distributed income applicable to common stockholders	3,363	2,545	6,719	6,943
Common Class A [Member] | Undistributed [Member]
Numerator:
Reallocation of income as a result of conversion of dilutive stock options	39	49	107	130
Reallocation of income due to conversion of Class B to Class A	2,688	2,637	7,196	7,122
Common Class A [Member]
Numerator:
Income from continuing operations applicable to common stockholders	27,831	20,073	70,063	51,525
Undistributed income from continuing operations applicable to common stockholders	24,801	17,861	64,032	45,536
Denominator:
Weighted average number of shares outstanding used to calculate basic income per share (in Shares)	23,304	22,139	23,137	22,195
Weighted average number of shares from stock options (in Shares)	371	478	383	473
Conversion of Class B to Class A common shares outstanding (in Shares)	2,562	3,330	2,639	3,535
Weighted average number of shares outstanding used to calculate diluted income per share from continuing operations (in Shares)	26,237	25,947	26,159	26,203
Diluted income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ 1.18	$ 0.89	$ 2.98	$ 2.28
Diluted distributed income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ (0.13)	$ (0.10)	$ (0.26)	$ (0.26)
Diluted undistributed income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ 1.05	$ 0.79	$ 2.72	$ 2.02
Basic income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ 1.19	$ 0.91	$ 3.03	$ 2.32
Basic distributed income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ (0.13)	$ (0.10)	$ (0.26)	$ (0.27)
Basic undistributed income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ 1.06	$ 0.81	$ 2.77	$ 2.05
Numerator:
Diluted undistributed income from continuing operations applicable to common stockholders	27,528	20,547	71,335	52,788
Common Class B [Member] | Basic [Member]
Numerator:
Distributed income applicable to common stockholders	(333)	(333)	(688)	(954)
Numerator:
Distributed income applicable to common stockholders	333	333	688	954
Common Class B [Member] | Distributed [Member]
Numerator:
Reallocation of income as a result of conversion of dilutive stock options	(5)	(6)	(10)	(17)
Common Class B [Member] | Diluted [Member]
Numerator:
Distributed income applicable to common stockholders	(328)	(327)	(678)	(937)
Numerator:
Distributed income applicable to common stockholders	328	327	678	937
Common Class B [Member] | Undistributed [Member]
Numerator:
Reallocation of income as a result of conversion of dilutive stock options	(39)	(49)	(107)	(130)
Common Class B [Member]
Numerator:
Income from continuing operations applicable to common stockholders	3,060	3,019	7,991	8,206
Undistributed income from continuing operations applicable to common stockholders	2,727	2,686	7,303	7,252
Denominator:
Weighted average number of shares outstanding used to calculate basic income per share (in Shares)	2,562	3,330	2,639	3,535
Weighted average number of shares outstanding used to calculate diluted income per share from continuing operations (in Shares)	2,562	3,330	2,639	3,535
Diluted income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ 1.18	$ 0.89	$ 2.98	$ 2.28
Diluted distributed income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ (0.13)	$ (0.10)	$ (0.26)	$ (0.26)
Diluted undistributed income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ 1.05	$ 0.79	$ 2.72	$ 2.02
Basic income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ 1.19	$ 0.91	$ 3.03	$ 2.32
Basic distributed income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ (0.13)	$ (0.10)	$ (0.26)	$ (0.27)
Basic undistributed income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ 1.06	$ 0.81	$ 2.77	$ 2.05
Numerator:
Diluted undistributed income from continuing operations applicable to common stockholders	$ 2,688	$ 2,637	$ 7,196	$ 7,122