Parent Company Financial Information (Condensed Statements of Income) (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Expenses:
Salaries									$ 2,222,000
Other operating expenses									11,755,000	$ 11,966,000	$ 12,066,000
Total noninterest expense									59,906,000	54,852,000	53,216,000
Income before income taxes	$ 11,921,000	$ 10,592,000	$ 12,054,000	$ 12,068,000	$ 8,632,000	$ 12,687,000	$ 11,714,000	$ 11,978,000	46,635,000	45,011,000	39,929,000
Income tax benefit	1,831,000	535,000	1,739,000	957,000	1,066,000	3,345,000	2,581,000	2,897,000	5,062,000	9,889,000	9,049,000
Net income	10,090,000	10,057,000	10,315,000	11,111,000	7,566,000	9,342,000	9,133,000	9,081,000	41,573,000	35,122,000	30,880,000
Comprehensive income	$ 12,118,000	$ 8,952,000	$ 7,869,000	$ 2,925,000	$ 6,939,000	$ 9,009,000	$ 11,619,000	$ 9,705,000	31,864,000	37,272,000	21,752,000
Parent Company [Member]
Income:
Dividends from subsidiary bank									15,525,000	11,150,000	4,500,000
Expenses:
Salaries									1,814,000	2,434,000	1,517,000
Other operating expenses									343,000	406,000	376,000
Total noninterest expense									2,157,000	2,840,000	1,893,000
Income before income taxes									13,368,000	8,310,000	2,607,000
Income tax benefit									(1,442,000)	(1,235,000)	(1,181,000)
Income before undistributed earnings of subsidiary bank									14,810,000	9,545,000	3,788,000
Equity in undistributed earnings									26,763,000	25,577,000	27,092,000
Net income									41,573,000	35,122,000	30,880,000
Comprehensive income									$ 31,864,000	$ 37,272,000	$ 21,752,000