Income Taxes (Deferred Tax Assets and Deferred Tax Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Allowance for loan losses and OREO reserves	$ 93,164	$ 127,078
Deferred compensation	16,703	25,824
Mortgage servicing assets	3,933	0
Unrealized losses on securities	16,084	21,568
State taxes	5,217	1,333
Interest income on nonaccrual loans	7,847	5,719
Other, net	6,322	7,419
Total gross deferred tax assets	149,270	188,941
Valuation allowance	(256)	(283)
Total deferred tax assets, net of valuation allowance	149,014	188,658
Deferred tax liabilities:
Core deposit intangibles	(6,525)	(12,642)
Investments in partnerships, tax credit and other investments, net	(3,813)	(1,694)
Fixed assets	(1,757)	(16,526)
Equipment financing	(25,604)	(15,106)
FHLB stock dividends	(1,868)	(1,524)
Acquired debt	(1,851)	(2,833)
Acquired loans and OREO	(3,412)	(7,055)
Prepaid expenses	(5,659)	(1,339)
Other, net	(1,119)	(241)
Total gross deferred tax liabilities	(51,608)	(58,960)
Net deferred tax assets	97,406	129,698
Federal
Deferred tax assets:
Allowance for loan losses and OREO reserves	62,942	97,921
Deferred compensation	11,483	20,093
Mortgage servicing assets	2,727	0
Unrealized losses on securities	10,730	16,253
State taxes	5,217	1,333
Interest income on nonaccrual loans	5,396	4,461
Other, net	744	2,053
Total gross deferred tax assets	99,239	142,114
Valuation allowance	0	0
Total deferred tax assets, net of valuation allowance	99,239	142,114
Deferred tax liabilities:
Core deposit intangibles	(4,408)	(9,768)
Investments in partnerships, tax credit and other investments, net	(10,838)	(7,012)
Fixed assets	(2,671)	(13,166)
Equipment financing	(21,844)	(13,240)
FHLB stock dividends	(1,285)	(1,189)
Acquired debt	(1,273)	(2,210)
Acquired loans and OREO	(2,252)	(5,407)
Prepaid expenses	(4,142)	(1,088)
Other, net	(510)	(121)
Total gross deferred tax liabilities	(49,223)	(53,201)
Net deferred tax assets	50,016	88,913
State
Deferred tax assets:
Allowance for loan losses and OREO reserves	28,857	27,792
Deferred compensation	5,220	5,731
Mortgage servicing assets	1,206	0
Unrealized losses on securities	5,354	5,315
State taxes	0	0
Interest income on nonaccrual loans	2,451	1,258
Other, net	5,481	5,269
Total gross deferred tax assets	48,569	45,365
Valuation allowance	(256)	(283)
Total deferred tax assets, net of valuation allowance	48,313	45,082
Deferred tax liabilities:
Core deposit intangibles	(2,117)	(2,874)
Investments in partnerships, tax credit and other investments, net	7,025	5,318
Fixed assets	914	(3,360)
Equipment financing	(3,760)	(1,866)
FHLB stock dividends	(583)	(335)
Acquired debt	(578)	(623)
Acquired loans and OREO	(754)	(1,242)
Prepaid expenses	(1,517)	(251)
Other, net	(609)	(120)
Total gross deferred tax liabilities	(1,979)	(5,353)
Net deferred tax assets	46,334	39,729
Foreign
Deferred tax assets:
Allowance for loan losses and OREO reserves	1,365	1,365
Deferred compensation	0	0
Mortgage servicing assets	0	0
Unrealized losses on securities	0	0
State taxes	0	0
Interest income on nonaccrual loans	0	0
Other, net	97	97
Total gross deferred tax assets	1,462	1,462
Valuation allowance	0	0
Total deferred tax assets, net of valuation allowance	1,462	1,462
Deferred tax liabilities:
Core deposit intangibles	0	0
Investments in partnerships, tax credit and other investments, net	0	0
Fixed assets	0	0
Equipment financing	0	0
FHLB stock dividends	0	0
Acquired debt	0	0
Acquired loans and OREO	(406)	(406)
Prepaid expenses	0	0
Other, net	0	0
Total gross deferred tax liabilities	(406)	(406)
Net deferred tax assets	$ 1,056	$ 1,056