Note 2 - Summary of Significant Accounting Policies (Detail) - Earnings per common share: (USD $) In Thousands, except Per 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
Net income, as reported (in Dollars)	$ 9,200	$ 9,365	$ 8,637	$ 7,129	$ 8,171	$ 10,150	$ 9,074	$ 7,953	$ 34,331	$ 35,348	$ 38,835
Divided by:
Weighted average common shares outstanding	30,310	30,432	30,472	30,396	30,371	30,679	30,823	30,620	30,402	30,623	30,336
Weighted average common stock equivalents									31	31	31
Total weighted average common shares outstanding and common stock equivalents	30,340	30,462	30,492	30,420	30,387	30,693	30,864	30,686	30,433	30,654	30,367
Basic earnings per common share (in Dollars per share)	$ 0.30	$ 0.31	$ 0.28	$ 0.23	$ 0.27	$ 0.33	$ 0.29	$ 0.26	$ 1.13	$ 1.15	$ 1.28
Diluted earnings per common share (in Dollars per share)	$ 0.30	$ 0.31	$ 0.28	$ 0.23	$ 0.27	$ 0.33	$ 0.29	$ 0.26	$ 1.13	$ 1.15	$ 1.28