Premises and Equipment - Summary of Premises and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Premises and Equipment [Line Items]
Total Cost	$ 228,827	$ 205,026
Accumulated Depreciation and Amortization	(132,975)	(110,594)
Net	95,852	94,432
Land
Premises and Equipment [Line Items]
Total Cost	22,042	25,035
Buildings and Leasehold Improvements
Premises and Equipment [Line Items]
Total Cost	124,441	114,444
Equipment
Premises and Equipment [Line Items]
Total Cost	$ 82,344	$ 65,547