Fair Value Measurements, Fair Value Of Financial Instruments as Measured On a Recurring Basis (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014		Jun. 30, 2014	Dec. 31, 2013		Sep. 30, 2013		Jun. 30, 2013	Dec. 31, 2012
Assets [Abstract]
Trading securities	$ 169,712			$ 91,616		$ 150,887
Available for sale securities	9,306,886			10,147,162		10,372,903
Fair value option securities	175,761			167,125		167,860
Mortgage servicing rights	173,286		155,740	153,333		140,863		132,889	100,812
Derviative Assets, Fair Value, Net of Cash Collateral, assets	360,809			265,012		377,325
Liabilities: [Abstract]
Derivative contracts net of cash margin, liabilities	348,687			247,185		232,544
U.S. Government agency debentures [Member]
Assets [Abstract]
Trading securities	41,004			34,120		74,632
U.S. agency residential mortgage-backed securities [Member]
Assets [Abstract]
Trading securities	33,226			21,011		26,129
Available for sale securities	6,850,603			7,716,010		7,981,387
Fair value option securities	175,761			157,431		163,567
Municipal and other tax-exempt securities [Member]
Assets [Abstract]
Trading securities	76,884			27,350		37,057
Available for sale securities	64,363			73,775		95,440
Other trading securities [Member]
Assets [Abstract]
Trading securities	18,598			9,135		13,069
U.S. Treasury [Member]
Assets [Abstract]
Available for sale securities	1,015			1,042		1,052
Privately issued residential mortgage-backed securities [Member]
Assets [Abstract]
Available for sale securities	171,493			221,099		230,900
Commercial mortgage-backed securities guaranteed by U.S. government agencies [Member]
Assets [Abstract]
Available for sale securities	2,141,645			2,055,804		1,946,295
Other debt securities [Member]
Assets [Abstract]
Available for sale securities	34,291			35,241		35,362
Fair value option securities	0			9,694		4,293
Perpetual preferred stock [Member]
Assets [Abstract]
Available for sale securities	24,358			22,863		23,680
Equity securities and mutual funds [Member]
Assets [Abstract]
Available for sale securities	19,118			21,328		58,787
Fair Value, Measurements, Recurring [Member]
Assets [Abstract]
Trading securities	169,712			91,616		150,887
Available for sale securities	9,306,886			10,147,162		10,372,903
Fair value option securities	175,761			167,125		167,860
Residential mortgage loans held for sale	373,253			200,546		230,511
Mortgage servicing rights	173,286	[1]		153,333	[1]	140,863	[1]
Derviative Assets, Fair Value, Net of Cash Collateral, assets	360,809	[2]		265,012	[3]	377,325	[4]
Other assets - private equity funds	27,118			27,341		27,799
Liabilities: [Abstract]
Derivative contracts net of cash margin, liabilities	348,687	[2]		247,185	[3]	232,544	[4]
Fair Value, Measurements, Recurring [Member] | U.S. Government agency debentures [Member]
Assets [Abstract]
Trading securities	41,004			34,120		74,632
Fair Value, Measurements, Recurring [Member] | U.S. agency residential mortgage-backed securities [Member]
Assets [Abstract]
Trading securities	33,226			21,011		26,129
Available for sale securities	6,850,603			7,716,010		7,981,387
Fair value option securities	175,761			157,431		163,567
Fair Value, Measurements, Recurring [Member] | Municipal and other tax-exempt securities [Member]
Assets [Abstract]
Trading securities	76,884			27,350		37,057
Available for sale securities	64,363			73,775		95,440
Fair Value, Measurements, Recurring [Member] | Other trading securities [Member]
Assets [Abstract]
Trading securities	18,598			9,135		13,069
Fair Value, Measurements, Recurring [Member] | U.S. Treasury [Member]
Assets [Abstract]
Available for sale securities	1,015			1,042		1,052
Fair Value, Measurements, Recurring [Member] | Privately issued residential mortgage-backed securities [Member]
Assets [Abstract]
Available for sale securities	171,493			221,099		230,900
Fair Value, Measurements, Recurring [Member] | Commercial mortgage-backed securities guaranteed by U.S. government agencies [Member]
Assets [Abstract]
Available for sale securities	2,141,645			2,055,804		1,946,295
Fair Value, Measurements, Recurring [Member] | Other debt securities [Member]
Assets [Abstract]
Available for sale securities	34,291			35,241		35,362
Fair value option securities	0			9,694		4,293
Fair Value, Measurements, Recurring [Member] | Perpetual preferred stock [Member]
Assets [Abstract]
Available for sale securities	24,358			22,863		23,680
Fair Value, Measurements, Recurring [Member] | Equity securities and mutual funds [Member]
Assets [Abstract]
Available for sale securities	19,118			21,328		58,787
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Assets [Abstract]
Trading securities	0			0		0
Available for sale securities	5,804			1,042		1,052
Fair value option securities	0			0		0
Residential mortgage loans held for sale	0			0		0
Mortgage servicing rights	0	[1]		0	[1]	0	[1]
Derviative Assets, Fair Value, Net of Cash Collateral, assets	10,799	[2]		2,712	[3]	644	[4]
Other assets - private equity funds	0			0		0
Liabilities: [Abstract]
Derivative contracts net of cash margin, liabilities	4,286	[2]		0	[3]	0	[4]
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | U.S. Government agency debentures [Member]
Assets [Abstract]
Trading securities	0			0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | U.S. agency residential mortgage-backed securities [Member]
Assets [Abstract]
Trading securities	0			0		0
Available for sale securities	0			0		0
Fair value option securities	0			0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Municipal and other tax-exempt securities [Member]
Assets [Abstract]
Trading securities	0			0		0
Available for sale securities	0			0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Other trading securities [Member]
Assets [Abstract]
Trading securities	0			0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | U.S. Treasury [Member]
Assets [Abstract]
Available for sale securities	1,015			1,042		1,052
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Privately issued residential mortgage-backed securities [Member]
Assets [Abstract]
Available for sale securities	0			0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Commercial mortgage-backed securities guaranteed by U.S. government agencies [Member]
Assets [Abstract]
Available for sale securities	0			0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Other debt securities [Member]
Assets [Abstract]
Available for sale securities	0			0		0
Fair value option securities	0			0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Perpetual preferred stock [Member]
Assets [Abstract]
Available for sale securities	0			0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Equity securities and mutual funds [Member]
Assets [Abstract]
Available for sale securities	4,789			0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Assets [Abstract]
Trading securities	169,712			91,616		150,887
Available for sale securities	9,286,739			10,119,396		10,323,261
Fair value option securities	175,761			167,125		167,860
Residential mortgage loans held for sale	365,877			200,546		230,511
Mortgage servicing rights	0	[1]		0	[1]	0	[1]
Derviative Assets, Fair Value, Net of Cash Collateral, assets	350,010	[2]		262,300	[3]	376,681	[4]
Other assets - private equity funds	0			0		0
Liabilities: [Abstract]
Derivative contracts net of cash margin, liabilities	344,401	[2]		247,185	[3]	232,544	[4]
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | U.S. Government agency debentures [Member]
Assets [Abstract]
Trading securities	41,004			34,120		74,632
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | U.S. agency residential mortgage-backed securities [Member]
Assets [Abstract]
Trading securities	33,226			21,011		26,129
Available for sale securities	6,850,603			7,716,010		7,981,387
Fair value option securities	175,761			157,431		163,567
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Municipal and other tax-exempt securities [Member]
Assets [Abstract]
Trading securities	76,884			27,350		37,057
Available for sale securities	54,170			55,970		55,769
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Other trading securities [Member]
Assets [Abstract]
Trading securities	18,598			9,135		13,069
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | U.S. Treasury [Member]
Assets [Abstract]
Available for sale securities	0			0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Privately issued residential mortgage-backed securities [Member]
Assets [Abstract]
Available for sale securities	171,493			221,099		230,900
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Commercial mortgage-backed securities guaranteed by U.S. government agencies [Member]
Assets [Abstract]
Available for sale securities	2,141,645			2,055,804		1,946,295
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Other debt securities [Member]
Assets [Abstract]
Available for sale securities	30,141			30,529		30,650
Fair value option securities	0			9,694		4,293
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Perpetual preferred stock [Member]
Assets [Abstract]
Available for sale securities	24,358			22,863		23,680
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Equity securities and mutual funds [Member]
Assets [Abstract]
Available for sale securities	14,329			17,121		54,580
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Assets [Abstract]
Trading securities	0			0		0
Available for sale securities	14,343			26,724		48,590
Fair value option securities	0			0		0
Residential mortgage loans held for sale	7,376			0		0
Mortgage servicing rights	173,286	[1]		153,333	[1]	140,863	[1]
Derviative Assets, Fair Value, Net of Cash Collateral, assets	0	[2]		0	[3]	0	[4]
Other assets - private equity funds	27,118			27,341		27,799
Liabilities: [Abstract]
Derivative contracts net of cash margin, liabilities	0	[2]		0	[3]	0	[4]
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | U.S. Government agency debentures [Member]
Assets [Abstract]
Trading securities	0			0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | U.S. agency residential mortgage-backed securities [Member]
Assets [Abstract]
Trading securities	0			0		0
Available for sale securities	0			0		0
Fair value option securities	0			0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Municipal and other tax-exempt securities [Member]
Assets [Abstract]
Trading securities	0			0		0
Available for sale securities	10,193			17,805		39,671
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Other trading securities [Member]
Assets [Abstract]
Trading securities	0			0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | U.S. Treasury [Member]
Assets [Abstract]
Available for sale securities	0			0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Privately issued residential mortgage-backed securities [Member]
Assets [Abstract]
Available for sale securities	0			0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Commercial mortgage-backed securities guaranteed by U.S. government agencies [Member]
Assets [Abstract]
Available for sale securities	0			0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Other debt securities [Member]
Assets [Abstract]
Available for sale securities	4,150			4,712		4,712
Fair value option securities	0			0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Perpetual preferred stock [Member]
Assets [Abstract]
Available for sale securities	0			0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Equity securities and mutual funds [Member]
Assets [Abstract]
Available for sale securities	$ 0			$ 4,207		$ 4,207

[1] A reconciliation of the beginning and ending fair value of mortgage servicing rights and disclosures of significant assumptions used to determine fair value are presented in Note 6, Mortgage Banking Activities.

[2] See Note 3 for detail of fair value of derivative contracts by contract type. Derivative contracts in asset positions that were valued based on quoted prices in active markets for identical instruments (Level 1) are primarily exchange-traded energy derivative contacts, net of cash margin. Derivative contacts in liability positions that were valued using quoted prices in active markets for identical instruments are exchange-traded interest rate and agricultural derivative contracts.

[3] See Note 3 for detail of fair value of derivative contracts by contract type. Derivative contracts based on quoted prices in active markets for identical instruments (Level 1) are exchange-traded energy derivative contacts, net of cash margin.

[4] See Note 3 for detail of fair value of derivative contracts by contract type. Derivative contracts based on quoted prices in active markets for identical instruments (Level 1) are exchange-traded energy and agricultural derivative contacts, net of cash margin.