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, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Numerator:
Income from continuing operations applicable to common stockholders	$ 34,537	$ 30,891	$ 94,401	$ 78,054
Denominator:
Weighted average number of shares outstanding used to calculate basic income per share (in Shares)	26,118	25,866	26,071	25,776
Weighted average number of shares outstanding used to calculate diluted income per share from continuing operations (in Shares)	26,359	26,237	26,337	26,159
Diluted income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ 1.31	$ 1.18	$ 3.58	$ 2.98
Basic income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ 1.32	$ 1.19	$ 3.62	$ 3.03
Common Class A [Member] | Equity Option [Member]
Antidilutive Securities
Shares issuable pursuant to stock options not included since they were antidilutive (in Shares)	13	14	13	17
Common Class A [Member] | Basic [Member]
Numerator:
Distributed income applicable to common stockholders	(3,765)	(3,030)	(10,578)	(6,031)
Numerator:
Distributed income applicable to common stockholders	3,765	3,030	10,578	6,031
Common Class A [Member] | Distributed [Member]
Numerator:
Reallocation of distributed income as a result of conversion of dilutive stock options	3	5	12	10
Reallocation of distributed income due to conversion of Class B to Class A common shares outstanding	406	328	1,141	678
Common Class A [Member] | Diluted [Member]
Numerator:
Diluted distributed income applicable to common stockholders	4,174	3,363	11,731	6,719
Common Class A [Member] | Undistributed [Member]
Numerator:
Reallocation of distributed income as a result of conversion of dilutive stock options	28	39	82	107
Reallocation of distributed income due to conversion of Class B to Class A common shares outstanding	2,951	2,688	8,042	7,196
Common Class A [Member]
Numerator:
Income from continuing operations applicable to common stockholders	31,149	27,831	85,124	70,063
Basic undistributed income from continuing operations applicable to common stockholders	27,384	24,801	74,546	64,032
Denominator:
Weighted average number of shares outstanding used to calculate basic income per share (in Shares)	23,556	23,304	23,509	23,137
Weighted average number of shares from stock options (in Shares)	241	371	266	383
Conversion of Class B to Class A common shares outstanding (in Shares)	2,562	2,562	2,562	2,639
Weighted average number of shares outstanding used to calculate diluted income per share from continuing operations (in Shares)	26,359	26,237	26,337	26,159
Diluted income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ 1.31	$ 1.18	$ 3.58	$ 2.98
Diluted distributed income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ (0.16)	$ (0.13)	$ (0.45)	$ (0.26)
Diluted undistributed income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ 1.15	$ 1.05	$ 3.13	$ 2.72
Basic income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ 1.32	$ 1.19	$ 3.62	$ 3.03
Basic distributed income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ (0.16)	$ (0.13)	$ (0.45)	$ (0.26)
Basic undistributed income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ 1.16	$ 1.06	$ 3.17	$ 2.77
Numerator:
Diluted distributed income applicable to common stockholders	30,363	27,528	82,670	71,335
Common Class B [Member] | Basic [Member]
Numerator:
Distributed income applicable to common stockholders	(409)	(333)	(1,153)	(688)
Numerator:
Distributed income applicable to common stockholders	409	333	1,153	688
Common Class B [Member] | Distributed [Member]
Numerator:
Reallocation of distributed income as a result of conversion of dilutive stock options	(3)	(5)	(12)	(10)
Common Class B [Member] | Diluted [Member]
Numerator:
Diluted distributed income applicable to common stockholders	406	328	1,141	678
Common Class B [Member] | Undistributed [Member]
Numerator:
Reallocation of distributed income as a result of conversion of dilutive stock options	(28)	(39)	(82)	(107)
Common Class B [Member]
Numerator:
Income from continuing operations applicable to common stockholders	3,388	3,060	9,277	7,991
Basic undistributed income from continuing operations applicable to common stockholders	2,979	2,727	8,124	7,303
Denominator:
Weighted average number of shares outstanding used to calculate basic income per share (in Shares)	2,562	2,562	2,562	2,639
Weighted average number of shares outstanding used to calculate diluted income per share from continuing operations (in Shares)	2,562	2,562	2,562	2,639
Diluted income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ 1.31	$ 1.18	$ 3.58	$ 2.98
Diluted distributed income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ (0.16)	$ (0.13)	$ (0.45)	$ (0.26)
Diluted undistributed income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ 1.15	$ 1.05	$ 3.13	$ 2.72
Basic income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ 1.32	$ 1.19	$ 3.62	$ 3.03
Basic distributed income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ (0.16)	$ (0.13)	$ (0.45)	$ (0.26)
Basic undistributed income per share from continuing operations applicable to common stockholders (in Dollars per share)	$ 1.16	$ 1.06	$ 3.17	$ 2.77
Numerator:
Diluted distributed income applicable to common stockholders	$ 2,951	$ 2,688	$ 8,042	$ 7,196