Fair Value Measurements, Fair Value Of Financial Instruments as Measured On a Recurring Basis (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014		Mar. 31, 2014	Dec. 31, 2013		Jun. 30, 2013		Mar. 31, 2013	Dec. 31, 2012
Assets [Abstract]
Trading securities	$ 101,097			$ 91,616		$ 190,591
Available for sale securities	9,699,146			10,147,162		10,698,074
Fair value option securities	185,674			167,125		205,756
Mortgage servicing rights	155,740		153,774	153,333		132,889		109,840	100,812
Derviative contracts, net of cash collateral, assets	357,680			265,012		546,206
Liabilities: [Abstract]
Derivative contracts net of cash margin, liabilities	297,851			247,185		521,991
U.S. Government agency debentures [Member]
Assets [Abstract]
Trading securities	19,027			34,120		60,713
U.S. agency residential mortgage-backed securities [Member]
Assets [Abstract]
Trading securities	13,540			21,011		43,858
Available for sale securities	7,259,504			7,716,010		8,372,795
Fair value option securities	181,205			157,431		203,816
Municipal and other tax-exempt securities [Member]
Assets [Abstract]
Trading securities	32,950			27,350		53,819
Available for sale securities	64,970			73,775		95,103
Other trading securities [Member]
Assets [Abstract]
Trading securities	35,580			9,135		32,201
U.S. Treasury [Member]
Assets [Abstract]
Available for sale securities	1,024			1,042		1,060
Privately issued residential mortgage-backed securities [Member]
Assets [Abstract]
Available for sale securities	179,042			221,099		297,175
Commercial mortgage-backed securities guaranteed by U.S. government agencies [Member]
Assets [Abstract]
Available for sale securities	2,115,295			2,055,804		1,846,943
Other debt securities [Member]
Assets [Abstract]
Available for sale securities	34,528			35,241		35,894
Fair value option securities	4,469			9,694		1,940
Perpetual preferred stock [Member]
Assets [Abstract]
Available for sale securities	24,730			22,863		25,583
Equity securities and mutual funds [Member]
Assets [Abstract]
Available for sale securities	20,053			21,328		23,521
Fair Value, Measurements, Recurring [Member]
Assets [Abstract]
Trading securities	101,097			91,616		190,591
Available for sale securities	9,699,146			10,147,162		10,698,074
Fair value option securities	185,674			167,125		205,756
Residential mortgage loans held for sale	325,875			200,546		301,057
Mortgage servicing rights	155,740	[1]		153,333	[1]	132,889	[1]
Derviative contracts, net of cash collateral, assets	357,680	[2]		265,012	[3]	546,206	[4]
Other assets - private equity funds	27,834			27,341		28,379
Liabilities: [Abstract]
Derivative contracts net of cash margin, liabilities	297,851	[2]		247,185	[3]	521,991	[4]
Fair Value, Measurements, Recurring [Member] | U.S. Government agency debentures [Member]
Assets [Abstract]
Trading securities	19,027			34,120		60,713
Fair Value, Measurements, Recurring [Member] | U.S. agency residential mortgage-backed securities [Member]
Assets [Abstract]
Trading securities	13,540			21,011		43,858
Available for sale securities	7,259,504			7,716,010		8,372,795
Fair value option securities	181,205			157,431		203,816
Fair Value, Measurements, Recurring [Member] | Municipal and other tax-exempt securities [Member]
Assets [Abstract]
Trading securities	32,950			27,350		53,819
Available for sale securities	64,970			73,775		95,103
Fair Value, Measurements, Recurring [Member] | Other trading securities [Member]
Assets [Abstract]
Trading securities	35,580			9,135		32,201
Fair Value, Measurements, Recurring [Member] | U.S. Treasury [Member]
Assets [Abstract]
Available for sale securities	1,024			1,042		1,060
Fair Value, Measurements, Recurring [Member] | Privately issued residential mortgage-backed securities [Member]
Assets [Abstract]
Available for sale securities	179,042			221,099		297,175
Fair Value, Measurements, Recurring [Member] | Commercial mortgage-backed securities guaranteed by U.S. government agencies [Member]
Assets [Abstract]
Available for sale securities	2,115,295			2,055,804		1,846,943
Fair Value, Measurements, Recurring [Member] | Other debt securities [Member]
Assets [Abstract]
Available for sale securities	34,528			35,241		35,894
Fair value option securities	4,469			9,694		1,940
Fair Value, Measurements, Recurring [Member] | Perpetual preferred stock [Member]
Assets [Abstract]
Available for sale securities	24,730			22,863		25,583
Fair Value, Measurements, Recurring [Member] | Equity securities and mutual funds [Member]
Assets [Abstract]
Available for sale securities	20,053			21,328		23,521
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Assets [Abstract]
Trading securities	0			0		0
Available for sale securities	6,130			1,042		6,179
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 contracts, net of cash collateral, assets	800	[2]		2,712	[3]	17,588	[4]
Other assets - private equity funds	0			0		0
Liabilities: [Abstract]
Derivative contracts net of cash margin, liabilities	0	[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	1,024			1,042		1,060
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	5,106			0		5,119
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Assets [Abstract]
Trading securities	101,097			91,616		190,591
Available for sale securities	9,678,340			10,119,396		10,645,608
Fair value option securities	185,674			167,125		205,756
Residential mortgage loans held for sale	325,875			200,546		301,057
Mortgage servicing rights	0	[1]		0	[1]	0	[1]
Derviative contracts, net of cash collateral, assets	356,880	[2]		262,300	[3]	528,618	[4]
Other assets - private equity funds	0			0		0
Liabilities: [Abstract]
Derivative contracts net of cash margin, liabilities	297,851	[2]		247,185	[3]	521,991	[4]
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | U.S. Government agency debentures [Member]
Assets [Abstract]
Trading securities	19,027			34,120		60,713
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | U.S. agency residential mortgage-backed securities [Member]
Assets [Abstract]
Trading securities	13,540			21,011		43,858
Available for sale securities	7,259,504			7,716,010		8,372,795
Fair value option securities	181,205			157,431		203,816
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Municipal and other tax-exempt securities [Member]
Assets [Abstract]
Trading securities	32,950			27,350		53,819
Available for sale securities	54,525			55,970		56,256
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Other trading securities [Member]
Assets [Abstract]
Trading securities	35,580			9,135		32,201
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	179,042			221,099		297,175
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	2,115,295			2,055,804		1,846,943
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Other debt securities [Member]
Assets [Abstract]
Available for sale securities	30,297			30,529		30,701
Fair value option securities	4,469			9,694		1,940
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Perpetual preferred stock [Member]
Assets [Abstract]
Available for sale securities	24,730			22,863		25,583
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Equity securities and mutual funds [Member]
Assets [Abstract]
Available for sale securities	14,947			17,121		16,155
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Assets [Abstract]
Trading securities	0			0		0
Available for sale securities	14,676			26,724		46,287
Fair value option securities	0			0		0
Residential mortgage loans held for sale	0			0		0
Mortgage servicing rights	155,740	[1]		153,333	[1]	132,889	[1]
Derviative contracts, net of cash collateral, assets	0	[2]		0	[3]	0	[4]
Other assets - private equity funds	27,834			27,341		28,379
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	10,445			17,805		38,847
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	4,231			4,712		5,193
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		$ 2,247

[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 exchange-traded energy derivative contacts, net of cash margin. Derivative contacts in liability positions that were valued using quoted prices in active market for identical instruments are exchange-traded energy, agricultural and interest rate derivative contracts that were fully offset by cash margin.

[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.