Premises and Equipment, Net - Premises and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Premises and Equipment, Net, by Type [Abstract]
Total cost of premises and equipment	$ 415,778	$ 418,563
Less accumulated depreciation and amortization	237,425	239,319
Premises and equipment, net	178,353	179,244
Assets held for sale	986	5,743
Total premises and equipment, net	179,339	184,987
Land [Member]
Premises and Equipment, Net, by Type [Abstract]
Total cost of premises and equipment	52,335	51,097
Building and Leasehold Improvements [Member]
Premises and Equipment, Net, by Type [Abstract]
Total cost of premises and equipment	197,372	195,296
Furniture and Equipment [Member]
Premises and Equipment, Net, by Type [Abstract]
Total cost of premises and equipment	$ 166,071	$ 172,170