Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Allowance for loan losses	$ 54,590	$ 51,842
Allowance for doubtful accounts	$ 1,436	$ 1,549
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, authorized shares (in shares)	50,000,000	50,000,000
Preferred stock, issued shares (in shares)	0	0
Preferred stock, outstanding shares (in shares)	0	0
Common Class A [Member]
Par value (in dollars per share)	$ 0.01	$ 0.01
Shares authorized (in shares)	600,000,000	600,000,000
Shares issued (in shares)	29,341,517	30,628,112
Shares outstanding (in shares)	29,341,517	30,628,112
Common Class B [Member]
Par value (in dollars per share)	$ 0.01	$ 0.01
Shares authorized (in shares)	60,000,000	60,000,000
Shares issued (in shares)	11,468,587	11,476,932
Shares outstanding (in shares)	11,468,587	11,476,932