Premises and Equipment and Leases Premises and Equipment and Leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Premises and Equipment [Line Items]
Premises and equipment	$ 779,050	$ 645,017
Less accumulated depreciation	243,531	314,984
Premises and equipment, net of accumulated depreciation	535,519	330,033
Depreciation Expense	51,600	51,200	$ 47,700
Operating Lease, Right-of-Use Asset	$ 180,000
Lease, Cost [Abstract]
Operating Lease, Weighted Average Remaining Lease Term	11 years 1 month 6 days
Operating Lease, Weighted Average Discount Rate, Percent	3.20%
Operating Lease, costs recognized as occupancy and equipment expense	$ 24,200
Operating Lease, operating cash flows	23,300
Lease, Cost	43,000	28,500	$ 27,500
Short-term Lease, Cost	12,600
Lessee, Operating Lease, Liability, Payment, Due [Abstract]
Operating Leases, Payments Due, Next Twelve Months	27,500
Operating Leases, Payments, Due in Two Years	25,700
Operating Leases, Payments, Due in Three Years	20,100
Operating Leases, Payments, Due in Four Years	18,900
Operating Lease, Payments, Due Year Five	18,200
Operating Leases, Payments, Due after Five Years	127,000
Land
Premises and Equipment [Line Items]
Premises and equipment	69,960	70,575
Buildings and improvements
Premises and Equipment [Line Items]
Premises and equipment	421,952	266,733
Software and related integration
Premises and Equipment [Line Items]
Premises and equipment	98,487	150,207
Furniture and equipment
Premises and Equipment [Line Items]
Premises and equipment	135,153	129,988
Construction in progress
Premises and Equipment [Line Items]
Premises and equipment	$ 53,498	$ 27,514