Note 22 - Parent Company Only Financial Information - Condensed Statements of Income (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Interest income									$ 24,489	$ 25,141	$ 24,827
Interest expense	$ (16,637)	$ (16,278)	$ (14,698)	$ (13,865)	$ (13,668)	$ (13,811)	$ (13,202)	$ (13,230)	(61,478)	(53,911)	(49,726)
Fair Value, Option, Changes in Fair Value, Gain (Loss)									(3,465)	(3,434)	(1,841)
Other operating expenses									(15,189)	(16,740)	(15,118)
Total income tax provision	7,693	5,291	6,775	5,254	8,116	6,655	20,717	5,615	25,013	41,103	27,167
Net income, as reported	$ 5,957	$ 10,179	$ 12,725	$ 12,260	$ 14,286	$ 10,634	$ 30,435	$ 9,561	41,121	64,916	46,209
Other comprehensive loss, net of tax									(624)	(2,800)	(2,655)
Comprehensive income									40,497	62,116	43,554
Holding Company [Member]
Dividends from the Bank									21,500	24,000	26,000
Interest income									505	247	242
Interest expense									(5,860)	(1,324)	(1,075)
Fair Value, Option, Changes in Fair Value, Gain (Loss)									(2,903)	(4,761)	(231)
Other operating expenses									(1,354)	(1,611)	(1,298)
Income before taxes and equity in undistributed earnings of subsidiary									11,888	16,551	23,638
Total income tax provision									6,926	3,198	687
Income before equity in undistributed earnings of subsidiary									18,814	19,749	24,325
Equity in undistributed earnings of the Bank									22,307	45,167	21,884
Net income, as reported									41,121	64,916	46,209
Other comprehensive loss, net of tax									(624)	(2,800)	(2,655)
Comprehensive income									$ 40,497	$ 62,116	$ 43,554