Income Taxes (Deferred Tax Assets and Deferred Tax Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Allowance for loan losses and OREO reserves	$ 98,242	$ 93,164
Tax credit carryforwards	26,831	0
Unrealized losses on securities	20,233	16,084
Deferred compensation	19,000	16,703
Interest income on nonaccrual loans	8,602	7,847
State taxes	4,898	5,217
Mortgage servicing assets	2,011	3,933
Fixed assets	885	0
Other, net	7,546	6,322
Total gross deferred tax assets	188,248	149,270
Valuation allowance	(128)	(256)
Total deferred tax assets, net of valuation allowance	188,120	149,014
Deferred tax liabilities:
Equipment financing	(30,523)	(25,604)
Investments in qualified affordable housing partnerships, tax credit and other investments, net	(27,292)	(3,813)
Core deposit intangibles	(4,542)	(6,525)
Acquired loans and OREO	(2,017)	(3,412)
FHLB stock dividends	(1,866)	(1,868)
Acquired debt	(1,771)	(1,851)
Prepaid expenses	(1,207)	(5,659)
Fixed assets	0	(1,757)
Other, net	(1,261)	(1,119)
Total gross deferred tax liabilities	(70,479)	(51,608)
Net deferred tax assets	117,641	97,406
Federal
Deferred tax assets:
Allowance for loan losses and OREO reserves	66,510	62,942
Tax credit carryforwards	24,116	0
Unrealized losses on securities	13,127	10,730
Deferred compensation	13,081	11,483
Interest income on nonaccrual loans	5,922	5,396
State taxes	4,898	5,217
Mortgage servicing assets	1,406	2,727
Fixed assets	(1,047)	0
Other, net	2,027	744
Total gross deferred tax assets	130,040	99,239
Valuation allowance	0	0
Total deferred tax assets, net of valuation allowance	130,040	99,239
Deferred tax liabilities:
Equipment financing	(26,040)	(21,844)
Investments in qualified affordable housing partnerships, tax credit and other investments, net	(31,098)	(10,838)
Core deposit intangibles	(3,048)	(4,408)
Acquired loans and OREO	(1,293)	(2,252)
FHLB stock dividends	(1,285)	(1,285)
Acquired debt	(1,219)	(1,273)
Prepaid expenses	(831)	(4,142)
Fixed assets	0	(2,671)
Other, net	(923)	(510)
Total gross deferred tax liabilities	(65,737)	(49,223)
Net deferred tax assets	64,303	50,016
State
Deferred tax assets:
Allowance for loan losses and OREO reserves	30,366	28,857
Tax credit carryforwards	2,715	0
Unrealized losses on securities	7,106	5,354
Deferred compensation	5,919	5,220
Interest income on nonaccrual loans	2,680	2,451
State taxes	0	0
Mortgage servicing assets	605	1,206
Fixed assets	1,932	0
Other, net	5,422	5,481
Total gross deferred tax assets	56,745	48,569
Valuation allowance	(128)	(256)
Total deferred tax assets, net of valuation allowance	56,617	48,313
Deferred tax liabilities:
Equipment financing	(4,483)	(3,760)
Investments in qualified affordable housing partnerships, tax credit and other investments, net	3,806	7,025
Core deposit intangibles	(1,494)	(2,117)
Acquired loans and OREO	(318)	(754)
FHLB stock dividends	(581)	(583)
Acquired debt	(552)	(578)
Prepaid expenses	(376)	(1,517)
Fixed assets	0	914
Other, net	(338)	(609)
Total gross deferred tax liabilities	(4,336)	(1,979)
Net deferred tax assets	52,281	46,334
Foreign
Deferred tax assets:
Allowance for loan losses and OREO reserves	1,366	1,365
Tax credit carryforwards	0	0
Unrealized losses on securities	0	0
Deferred compensation	0	0
Interest income on nonaccrual loans	0	0
State taxes	0	0
Mortgage servicing assets	0	0
Fixed assets	0	0
Other, net	97	97
Total gross deferred tax assets	1,463	1,462
Valuation allowance	0	0
Total deferred tax assets, net of valuation allowance	1,463	1,462
Deferred tax liabilities:
Equipment financing	0	0
Investments in qualified affordable housing partnerships, tax credit and other investments, net	0	0
Core deposit intangibles	0	0
Acquired loans and OREO	(406)	(406)
FHLB stock dividends	0	0
Acquired debt	0	0
Prepaid expenses	0	0
Fixed assets	0	0
Other, net	0	0
Total gross deferred tax liabilities	(406)	(406)
Net deferred tax assets	$ 1,057	$ 1,056