Premises and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 240,253	$ 214,027
Less accumulated depreciation and amortization	(70,763)	(63,685)
Total	169,490	150,342
Depreciation and amortization expense	9,800	11,800	$ 12,300
Land [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	54,510	47,438
Building [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	110,216	101,196
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	24,184	19,491
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	30,486	26,709
Vehicles [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	473	536
Software [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 20,384	$ 18,657