Premises and Equipment - Components and Depreciation and Amortization Expenses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Components of premises and equipment
Premises and equipment	$ 498,216	$ 490,231
Less: Accumulated depreciation and amortization	197,428	185,127
Net book value	300,788	305,104
Depreciation and amortization expenses	14,799	14,546	$ 13,124
Occupancy
Components of premises and equipment
Depreciation and amortization expenses	8,901	9,039	8,540
Equipment
Components of premises and equipment
Depreciation and amortization expenses	5,898	5,507	$ 4,584
Buildings
Components of premises and equipment
Premises and equipment	279,563	277,133
Furniture and equipment
Components of premises and equipment
Premises and equipment	76,832	74,965
Land
Components of premises and equipment
Premises and equipment	89,164	89,164
Leasehold improvements
Components of premises and equipment
Premises and equipment	$ 52,657	$ 48,969