Fair Value Measurements, Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	$ 1,623,921	$ 1,956,923
Investment securities	293,418	355,187
Available for sale securities	11,269,643	8,857,120
Fair value option securities	1,098,577	283,235
Residential mortgage loans held for sale	182,271	149,221
Loans	21,750,987	21,656,730
Allowance for loan losses	(210,759)	(207,457)	$ (230,682)	$ (246,159)
Loans, net of allowance	21,540,228	21,449,273
Mortgage servicing rights	201,886	259,254	252,867	247,073
Derivative contracts, net of cash margin, Assets, Fair Value	323,375	320,929
Time deposits	2,217,849	2,113,380
Subordinated debentures	275,923	275,913
Derivative contracts, net of cash margin, Liabilities, Fair Value	251,128	362,306
Commercial [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	14,031,650	13,636,078
Allowance for loan losses	(118,187)	(102,226)	(124,269)	(140,213)
Commercial Real Estate [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	4,433,783	4,764,813
Allowance for loan losses	(51,805)	(60,026)	(56,621)	(50,749)
Residential Mortgage [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	2,084,172	2,230,033
Allowance for loan losses	(14,400)	(17,964)	(18,451)	(18,224)
Personal [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	1,201,382	1,025,806
Allowance for loan losses	(9,172)	(9,473)	$ (9,124)	$ (8,773)
U.S. government agency debentures [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	44,264	63,765
Residential agency mortgage-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	1,504,651	1,791,584
Investment securities	10,676	12,612
Available for sale securities	8,046,096	5,804,708
Fair value option securities	1,088,660	283,235
Municipal and other tax-exempt securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	26,196	34,507
Investment securities	93,653	137,296
Available for sale securities	1,861	2,864
U.S. Treasury [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	1,600	493
Fair value option securities	9,917	0
Residential non-agency mortgage-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	41,609	59,736
Commercial agency mortgage-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	3,178,005	2,953,889
Other debt securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	34,726	24,411
Investment securities	189,089	205,279
Available for sale securities	472	35,430
Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	735,836	741,749
Interest-bearing cash and cash equivalents	522,985	401,675
Trading securities	1,623,921	1,956,923
Investment securities	314,402	367,298
Available for sale securities	11,269,643	8,857,120
Fair value option securities	1,098,577
Residential mortgage loans held for sale	182,271	149,221
Loans	21,689,329	21,478,228
Allowance for loan losses	0	0
Loans, net of allowance	21,689,329	21,478,228
Mortgage servicing rights	201,886	259,254
Derivative contracts, net of cash margin, Assets, Fair Value	323,375	320,929
Deposits with no stated maturity	25,403,319	23,150,383
Time deposits	2,212,467	2,073,538
Other borrowed funds	8,315,860	7,071,953
Subordinated debentures	284,627	261,977
Derivative contracts, net of cash margin, Liabilities, Fair Value	251,128	362,306
Estimate of Fair Value Measurement [Member] | Commercial [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	13,966,221	13,526,162
Estimate of Fair Value Measurement [Member] | Commercial Real Estate [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	4,422,717	4,713,747
Estimate of Fair Value Measurement [Member] | Residential Mortgage [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	2,098,093	2,213,951
Estimate of Fair Value Measurement [Member] | Personal [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	1,202,298	1,024,368
Estimate of Fair Value Measurement [Member] | U.S. government agency debentures [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	44,264	63,765
Estimate of Fair Value Measurement [Member] | Residential agency mortgage-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	1,504,651	1,791,584
Investment securities	11,164	12,770
Available for sale securities	8,046,096	5,804,708
Fair value option securities	1,088,660	283,235
Estimate of Fair Value Measurement [Member] | Municipal and other tax-exempt securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	26,196	34,507
Investment securities	96,897	138,562
Available for sale securities	1,861	2,864
Estimate of Fair Value Measurement [Member] | Asset-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	14,084	42,656
Estimate of Fair Value Measurement [Member] | Other trading securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	34,726	24,411
Estimate of Fair Value Measurement [Member] | U.S. Treasury [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	1,600	493
Fair value option securities	9,917
Estimate of Fair Value Measurement [Member] | Residential non-agency mortgage-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	41,609	59,736
Estimate of Fair Value Measurement [Member] | Commercial agency mortgage-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	3,178,005	2,953,889
Estimate of Fair Value Measurement [Member] | Other debt securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities	206,341	215,966
Available for sale securities	472	35,430
Carrying (Reported) Amount, Fair Value Disclosure [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	735,836	741,749
Interest-bearing cash and cash equivalents	522,985	401,675
Trading securities	1,623,921	1,956,923
Investment securities	293,418	355,187
Available for sale securities	11,269,643	8,857,120
Fair value option securities	1,098,577
Residential mortgage loans held for sale	182,271	149,221
Loans	21,750,987	21,656,730
Allowance for loan losses	(210,759)	(207,457)
Loans, net of allowance	21,540,228	21,449,273
Mortgage servicing rights	201,886	259,254
Derivative contracts, net of cash margin, Assets, Fair Value	323,375	320,929
Deposits with no stated maturity	25,403,319	23,150,383
Time deposits	2,217,849	2,113,380
Other borrowed funds	8,345,405	7,142,801
Subordinated debentures	275,923	275,913
Derivative contracts, net of cash margin, Liabilities, Fair Value	251,128	362,306
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Commercial [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	14,031,650	13,636,078
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Commercial Real Estate [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	4,433,783	4,764,813
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Residential Mortgage [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	2,084,172	2,230,033
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Personal [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	1,201,382	1,025,806
Carrying (Reported) Amount, Fair Value Disclosure [Member] | U.S. government agency debentures [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	44,264	63,765
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Residential agency mortgage-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	1,504,651	1,791,584
Investment securities	10,676	12,612
Available for sale securities	8,046,096	5,804,708
Fair value option securities	1,088,660	283,235
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Municipal and other tax-exempt securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	26,196	34,507
Investment securities	93,653	137,296
Available for sale securities	1,861	2,864
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Asset-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	14,084	42,656
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Other trading securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	34,726	24,411
Carrying (Reported) Amount, Fair Value Disclosure [Member] | U.S. Treasury [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	1,600	493
Fair value option securities	9,917
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Residential non-agency mortgage-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	41,609	59,736
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Commercial agency mortgage-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	3,178,005	2,953,889
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Other debt securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities	189,089	205,279
Available for sale securities	472	35,430
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	735,836	741,749
Interest-bearing cash and cash equivalents	522,985	401,675
Trading securities	0	0
Investment securities	0	0
Available for sale securities	1,600	493
Fair value option securities	9,917
Residential mortgage loans held for sale	0	0
Loans	0	0
Allowance for loan losses	0	0
Loans, net of allowance	0	0
Mortgage servicing rights	0	0
Derivative contracts, net of cash margin, Assets, Fair Value	8,944	44,074
Deposits with no stated maturity	0	0
Time deposits	0	0
Other borrowed funds	0	0
Subordinated debentures	0	0
Derivative contracts, net of cash margin, Liabilities, Fair Value	0	0
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value Measurement [Member] | Commercial [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	0	0
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value Measurement [Member] | Commercial Real Estate [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	0	0
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value Measurement [Member] | Residential Mortgage [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	0	0
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value Measurement [Member] | Personal [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	0	0
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value Measurement [Member] | U.S. government agency debentures [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	0	0
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value Measurement [Member] | Residential agency mortgage-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	0	0
Investment securities	0	0
Available for sale securities	0	0
Fair value option securities	0	0
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value Measurement [Member] | Municipal and other tax-exempt securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	0	0
Investment securities	0	0
Available for sale securities	0	0
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value Measurement [Member] | Asset-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	0	0
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value Measurement [Member] | Other trading securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	0	0
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value Measurement [Member] | U.S. Treasury [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	1,600	493
Fair value option securities	9,917
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value Measurement [Member] | Residential non-agency mortgage-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	0	0
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value Measurement [Member] | Commercial agency mortgage-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	0	0
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value Measurement [Member] | Other debt securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities	0	0
Available for sale securities	0	0
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	0	0
Interest-bearing cash and cash equivalents	0	0
Trading securities	1,623,921	1,956,923
Investment securities	116,267	159,237
Available for sale securities	11,267,571	8,856,155
Fair value option securities	1,088,660
Residential mortgage loans held for sale	173,958	134,014
Loans	0	0
Allowance for loan losses	0	0
Loans, net of allowance	0	0
Mortgage servicing rights	0	0
Derivative contracts, net of cash margin, Assets, Fair Value	314,431	276,855
Deposits with no stated maturity	0	0
Time deposits	0	0
Other borrowed funds	0	0
Subordinated debentures	284,627	261,977
Derivative contracts, net of cash margin, Liabilities, Fair Value	251,128	362,306
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member] | Commercial [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	0	0
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member] | Commercial Real Estate [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	0	0
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member] | Residential Mortgage [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	0	0
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member] | Personal [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	0	0
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member] | U.S. government agency debentures [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	44,264	63,765
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member] | Residential agency mortgage-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	1,504,651	1,791,584
Investment securities	11,164	12,770
Available for sale securities	8,046,096	5,804,708
Fair value option securities	1,088,660	283,235
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member] | Municipal and other tax-exempt securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	26,196	34,507
Investment securities	96,897	138,562
Available for sale securities	1,861	2,864
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member] | Asset-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	14,084	42,656
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member] | Other trading securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	34,726	24,411
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member] | U.S. Treasury [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	0	0
Fair value option securities	0
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member] | Residential non-agency mortgage-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	41,609	59,736
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member] | Commercial agency mortgage-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	3,178,005	2,953,889
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member] | Other debt securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities	8,206	7,905
Available for sale securities	0	34,958
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	0	0
Interest-bearing cash and cash equivalents	0	0
Trading securities	0	0
Investment securities	198,135	208,061
Available for sale securities	472	472
Fair value option securities	0
Residential mortgage loans held for sale	8,313	15,207
Loans	21,689,329	21,478,228
Allowance for loan losses	0	0
Loans, net of allowance	21,689,329	21,478,228
Mortgage servicing rights	201,886	259,254
Derivative contracts, net of cash margin, Assets, Fair Value	0	0
Deposits with no stated maturity	25,403,319	23,150,383
Time deposits	2,212,467	2,073,538
Other borrowed funds	8,315,860	7,071,953
Subordinated debentures	0	0
Derivative contracts, net of cash margin, Liabilities, Fair Value	0	0
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member] | Commercial [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	13,966,221	13,526,162
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member] | Commercial Real Estate [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	4,422,717	4,713,747
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member] | Residential Mortgage [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	2,098,093	2,213,951
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member] | Personal [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	1,202,298	1,024,368
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member] | U.S. government agency debentures [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	0	0
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member] | Residential agency mortgage-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	0	0
Investment securities	0	0
Available for sale securities	0	0
Fair value option securities	0	0
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member] | Municipal and other tax-exempt securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	0	0
Investment securities	0	0
Available for sale securities	0	0
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member] | Asset-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	0	0
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member] | Other trading securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	0	0
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member] | U.S. Treasury [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	0	0
Fair value option securities	0
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member] | Residential non-agency mortgage-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	0	0
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member] | Commercial agency mortgage-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	0	0
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member] | Other debt securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities	198,135	208,061
Available for sale securities	$ 472	$ 472