CONSOLIDATED STATEMENTS OF INCOME - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
INTEREST INCOME:
Loans, including fees	$ 164,232,000	$ 133,958,000	$ 123,360,000
Taxable investment securities	7,876,000	7,046,000	7,481,000
Federal Home Loan Bank stock and other	1,884,000	1,428,000	1,536,000
Total interest income	173,992,000	142,432,000	132,377,000
INTEREST EXPENSE:
Deposits	6,058,000	4,380,000	3,905,000
Securities sold under agreements to repurchase and other short-term borrowings	65,000	92,000	112,000
Federal Home Loan Bank advances	10,900,000	11,934,000	13,072,000
Subordinated note	915,000	2,056,000	2,515,000
Total interest expense	17,938,000	18,462,000	19,604,000
NET INTEREST INCOME	156,054,000	123,970,000	112,773,000
Provision for loan and lease losses	14,493,000	5,396,000	2,859,000
NET INTEREST INCOME AFTER PROVISION FOR LOAN AND LEASE LOSSES	141,561,000	118,574,000	109,914,000
NONINTEREST INCOME:
Service charges on deposit accounts	13,176,000	13,015,000	13,807,000
Net refund transfer fees	19,240,000	17,388,000	16,130,000
Mortgage banking income	6,882,000	4,411,000	2,862,000
Interchange fee income	9,009,000	8,353,000	7,017,000
Program fees	3,044,000	1,233,000	591,000
Increase in cash surrender value of bank owned life insurance	1,516,000	1,402,000	1,329,000
Gain on call of securities available for sale		88,000
Net gains (losses) on other real estate owned	244,000	(301,000)	(2,218,000)
Other	4,398,000	2,405,000	3,001,000
Total noninterest income	57,509,000	47,994,000	42,519,000
NONINTEREST EXPENSES:
Salaries and employee benefits	69,882,000	58,091,000	54,373,000
Occupancy and equipment, net	21,777,000	20,689,000	22,008,000
Communication and transportation	4,256,000	3,752,000	3,866,000
Marketing and development	3,778,000	3,161,000	3,264,000
FDIC insurance expense	1,780,000	2,084,000	1,865,000
Bank franchise tax expense	4,757,000	4,734,000	4,616,000
Data processing	6,121,000	4,340,000	3,513,000
Interchange related expense	4,140,000	3,873,000	3,450,000
Supplies	1,406,000	1,101,000	1,009,000
Other real estate owned expense	503,000	735,000	1,024,000
Legal and professional fees	2,556,000	3,306,000	2,766,000
FHLB advance prepayment penalty	846,000	0	0
Other	8,305,000	7,458,000	6,364,000
Total noninterest expenses	130,107,000	113,324,000	108,118,000
INCOME BEFORE INCOME TAX EXPENSE	68,963,000	53,244,000	44,315,000
INCOME TAX EXPENSE	23,060,000	18,078,000	15,528,000
NET INCOME	$ 45,903,000	$ 35,166,000	$ 28,787,000
Class A Common Stock
BASIC EARNINGS PER SHARE:
Basic earnings per share (in dollars per share)	$ 2.22	$ 1.70	$ 1.39
DILUTED EARNINGS PER SHARE:
Diluted earnings per share (in dollars per share)	2.22	1.70	1.38
DIVIDENDS DECLARED PER COMMON SHARE:
Dividend declared per common share (in dollars per share)	0.825	0.781	0.737
Class B Common Stock
BASIC EARNINGS PER SHARE:
Basic earnings per share (in dollars per share)	2.02	1.55	1.32
DILUTED EARNINGS PER SHARE:
Diluted earnings per share (in dollars per share)	2.01	1.54	1.32
DIVIDENDS DECLARED PER COMMON SHARE:
Dividend declared per common share (in dollars per share)	$ 0.750	$ 0.710	$ 0.670