Premises and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Total premises and equipment, gross	$ 272,303	$ 226,699
Less accumulated depreciation	(127,291)	(120,382)
Premises and equipment, net	145,012	106,317
Net rent expense under operating leases	3,300	1,700	$ 1,200
Closed branch offices transferred to other assets	4,846	2,692	$ 841
Land and land improvements
Property, Plant and Equipment [Line Items]
Total premises and equipment, gross	36,185	28,447
Buildings
Property, Plant and Equipment [Line Items]
Total premises and equipment, gross	144,155	120,370
Furniture and equipment
Property, Plant and Equipment [Line Items]
Total premises and equipment, gross	$ 91,963	$ 77,882