Bank Premises and Equipment - Summary of Bank Premises and Equipment (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Property, Plant and Equipment [Line Items]
Cost	$ 81,395	$ 71,785
Accumulated Depreciation & Amortization	(36,309)	(37,280)
Net Carrying Value	45,086	34,505
Premises [Member]
Property, Plant and Equipment [Line Items]
Cost	59,471	49,647
Accumulated Depreciation & Amortization	(20,260)	(20,518)
Net Carrying Value	39,211	29,129
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Cost	21,924	22,138
Accumulated Depreciation & Amortization	(16,049)	(16,762)
Net Carrying Value	$ 5,875	$ 5,376