Premises and Equipment - Schedule of Premises and Equipment and Related Accumulated Depreciation (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property Plant And Equipment [Line Items]
Premises and equipment, gross	$ 126,880	$ 107,664
Less: accumulated depreciation	(45,303)	(41,013)
Total Premises and Equipment	81,577	66,651
Land
Property Plant And Equipment [Line Items]
Premises and equipment, gross	22,108	18,698
Premises
Property Plant And Equipment [Line Items]
Premises and equipment, gross	57,719	44,301
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Premises and equipment, gross	22,292	21,700
Leasehold Improvements
Property Plant And Equipment [Line Items]
Premises and equipment, gross	10,740	10,515
Equipment
Property Plant And Equipment [Line Items]
Premises and equipment, gross	12,525	11,583
Construction In Process
Property Plant And Equipment [Line Items]
Premises and equipment, gross	$ 1,496	$ 867