Note 7 - Earnings per Share (Detail) - Summary of Earnings and Weighted Average Number of Common Shares Used in the Calculation of Basic and Diluted Earnings Per Share (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Basic:
Weighted average common shares outstanding, basic									13,852,709	13,774,628	13,671,053
Net income (in Dollars)	$ 14,434	$ 17,233	$ 13,614	$ 12,676	$ 14,526	$ 17,211	$ 13,611	$ 18,724	$ 57,957	$ 64,072	$ 52,695
Dividends to preferred stockholders (in Dollars)									8,671	8,671	8,673
Net income available to common stockholders (in Dollars)	12,266	15,066	11,446	10,508	12,358	15,044	11,443	16,556	49,286	55,401	44,022
Earnings per common share, basic (in Dollars per share)	$ 0.88	$ 1.09	$ 0.83	$ 0.76	$ 0.89	$ 1.09	$ 0.83	$ 1.21	$ 3.56	$ 4.02	$ 3.22
Diluted:
Dilutive effect of contingent issuable stock									109,233
Convertible preferred stock									2,623,329	2,623,452
Assumed average common shares outstanding									16,598,816	16,414,023	13,676,476
Add dilutive preferred stock dividends for effect of assumed conversion of preferred stock (in Dollars)									8,671	8,671
Net income for diluted earnings per common share (in Dollars)									$ 57,957	$ 64,072	$ 44,022
Earnings per common share, diluted (in Dollars per share)	$ 0.87	$ 1.04	$ 0.82	$ 0.76	$ 0.88	$ 1.05	$ 0.83	$ 1.15	$ 3.49	$ 3.90	$ 3.22
Stock Options [Member]
Diluted:
Dilutive effect of securities									8,019	9,934	3,237
Restricted Stock [Member]
Diluted:
Dilutive effect of securities									5,526	6,009	2,186