Premises and Equipment Premises and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Premises and Equipment [Line Items]
Premises and equipment	$ 733,160	$ 674,870
Less accumulated depreciation	407,311	368,380
Premises and equipment, net of accumulated depreciation	325,849	306,490
Depreciation Expense	40,000	34,000	$ 33,000
Land
Premises and Equipment [Line Items]
Premises and equipment	70,552	72,612
Buildings and improvements
Premises and Equipment [Line Items]
Premises and equipment	250,311	225,181
Software
Premises and Equipment [Line Items]
Premises and equipment	158,155	142,476
Furniture and equipment
Premises and Equipment [Line Items]
Premises and equipment	217,399	194,715
Construction in progress
Premises and Equipment [Line Items]
Premises and equipment	$ 36,743	$ 39,886