Premises, Furniture and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Total	$ 289,543	$ 267,948
Less accumulated depreciation	(102,125)	(95,624)
Premises, furniture and equipment, net	187,418	172,324
Depreciation expense	11,700	11,100	$ 10,400
Land and land improvements
Property, Plant and Equipment [Line Items]
Total	52,442	48,621
Buildings and building improvements
Property, Plant and Equipment [Line Items]
Total	170,160	155,209
Depreciation expense	5,800	5,200	4,900
Furniture and equipment
Property, Plant and Equipment [Line Items]
Total	66,941	64,118
Depreciation expense	$ 6,000	$ 6,000	$ 5,500