Mortgage Servicing Rights Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Servicing Assets at Amortized Value [Line Items]
Loans serviced by unrelated third party	$ 4,700,000	$ 4,900,000
Estimated fair value of MSRs	28,200	45,200
Non-interest income before investment securities gains	226,335	211,427	$ 195,488
Mortgage banking
Servicing Assets at Amortized Value [Line Items]
Non-interest income before investment securities gains	42,309	23,099	19,026
Residential Mortgage
Servicing Assets at Amortized Value [Line Items]
Estimated fair value of MSRs	28,245	45,193	50,200
Valuation Allowance for Impairment of Recognized Servicing Assets, Balance	(10,500)	0	0	$ 0
Amortization expense	12,695	6,852	5,846
Residential Mortgage | Mortgage banking
Servicing Assets at Amortized Value [Line Items]
Non-interest income before investment securities gains	$ 11,900	$ 12,000	$ 11,800