Premises and Equipment, Net of Accumulated Depreciation (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Premises and Equipment, Net of Accumulated Depreciation
Accumulated depreciation	$ (92,944)	$ (90,238)
Premises and Equipment, Net	167,671	158,989
Land
Premises and Equipment, Net of Accumulated Depreciation
Premises and equipment, gross	27,260	25,027
Office buildings and construction in progress
Premises and Equipment, Net of Accumulated Depreciation
Premises and equipment, gross	159,391	153,340
Furniture, fixtures and equipment
Premises and Equipment, Net of Accumulated Depreciation
Premises and equipment, gross	66,375	63,467
Leasehold improvements
Premises and Equipment, Net of Accumulated Depreciation
Premises and equipment, gross	$ 7,589	$ 7,393