Income Taxes (Deferred Tax Assets and Deferred Tax Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Allowance for loan losses	$ 109,903	$ 96,876
Investments in qualified affordable housing partnerships, tax credit and other investments, net	11,190	3,691
Deferred compensation	23,816	18,724
Interest income on nonaccrual loans	9,527	8,602
State taxes	5,848	4,506
Unrealized gains/losses on securities	324	20,233
Tax credit carryforwards	0	26,831
Premises and equipment	1,578	1,887
Deferred gain	0	4,476
Lease liability	35,948	2,604
Other	641	6,178
Total gross deferred tax assets	198,775	194,608
Valuation allowance	(21)	(128)
Total deferred tax assets, net of valuation allowance	198,754	194,480
Deferred tax liabilities:
Equipment lease financing	30,669	30,523
Investments in qualified affordable housing partnerships, tax credit and other investments, net	12,301	30,706
Core deposit intangibles	3,032	4,427
FHLB stock dividends	1,854	1,866
Mortgage servicing assets	1,839	2,390
Acquired debt	1,679	1,771
Prepaid expenses	1,100	1,207
Premises and equipment	1,890	1,078
Operating lease right-of-use assets	34,313
Other	3,590	2,872
Total gross deferred tax liabilities	92,267	76,840
Net deferred tax assets	$ 106,487	$ 117,640