Fair Value Measurements, Fair Value Of Financial Instruments as Measured On a Recurring Basis (Details) (USD $)	6 Months Ended		12 Months Ended
	Jun. 30, 2011		Dec. 31, 2010		Mar. 31, 2011	Jun. 30, 2010		Mar. 31, 2010	Dec. 31, 2009
Assets [Abstract]
Trading securities	$ 99,846,000		$ 55,467,000			$ 62,159,000
Available for sale securities [Abstract]
Mortgage trading securities	553,231,000		428,021,000			534,641,000
Residential mortgage loans held for sale	169,609,000		263,413,000			227,574,000
Mortgage servicing rights	109,192,000		115,723,000		120,345,000	98,942,000		119,066,000	73,824,000
Derivative contracts, assets	229,887,000		270,445,000			334,576,000
Liabilities [Abstract]
Derivative contracts, liabilities	173,917,000		215,420,000			299,851,000
Investment grade taxable securities par rate of yield, lower range (in hundredths)	1.69%
Investment grade taxable securities par rate of yield, upper range (in hundredths)	1.75%
Average yields on comparable short-term taxable securities, maximum	1.00%
Investment grade tax-exempt securities par rate of yield, minimum (in hundredths)	1.05%
Investment grade tax-exempt securities par rate of yield, maximum (in hundredths)	1.35%
Investment grade tax-exempt securities yield spread over comparable securities, minimum (in basis points)	75
Investment grade tax-exempt securities yield spread over comparable securities, maximum (in basis points)	80
Percentage of estimated fair value to par value of tax-exempt securities rated investment grade, minimum (in hundredths)	98.89%
Percentage of estimated fair value to par value of tax-exempt securities rated investment grade, maximum (in hundredths)	99.34%
Municipal and tax-exempt securities rated below investment grade	14,000,000
Below investment grade tax-exempt securities par rate of yield, minimum (in hundredths)	6.23%
Below investment grade tax-exempt securities par rate of yield, maximum (in hundredths)	10.30%
Below investment grade tax-exempt securities yield spread over comparable securities (in basis points)	600		525
Percentage of estimated fair value to par value of tax exempt securities rated below investment grade minimum	82.66%
Percentage of estimated fair value to par value of tax exempt securities rated below investment grade maximum	82.83%
Fair Value, Measurements, Recurring [Member]
Assets [Abstract]
Trading securities	99,846,000		55,467,000			62,159,000
Available for sale securities [Abstract]
U.S. Treasury	1,003,000
Municipal and other tax-exempt	70,210,000		72,942,000			66,439,000
U.S. agency residential mortgage-backed securities	8,893,789,000		8,446,908,000			8,223,719,000
Private issue residential mortgage-backed securities	513,222,000		644,210,000			735,516,000
Other debt securities	5,893,000		6,401,000			13,064,000
Perpetual preferred stock	22,694,000		22,114,000			19,881,000
Equity securities and mutual funds	60,197,000		43,046,000			47,209,000
Total available for sale securities	9,567,008,000		9,235,621,000			9,105,828,000
Mortgage trading securities	553,231,000		428,021,000			534,641,000
Residential mortgage loans held for sale	169,609,000		263,413,000			227,574,000
Mortgage servicing rights	109,192,000		115,723,000			98,942,000
Derivative contracts, assets	229,887,000	[1]	270,445,000	[1]		334,576,000	[1]
Other assets - private equity funds	28,313,000		25,436,000			23,834,000
Liabilities [Abstract]
Certificates of deposit			27,414,000			27,957,000
Derivative contracts, liabilities	173,917,000		215,420,000			299,851,000
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Assets [Abstract]
Trading securities	2,327,000		877,000			4,030,000
Available for sale securities [Abstract]
U.S. Treasury	1,003,000
Municipal and other tax-exempt	0		0			0
U.S. agency residential mortgage-backed securities	0		0			0
Private issue residential mortgage-backed securities	0		0			0
Other debt securities	0		0			0
Perpetual preferred stock	0		0			0
Equity securities and mutual funds	41,557,000		22,344,000			22,728,000
Total available for sale securities	42,560,000		22,344,000			22,728,000
Mortgage trading securities	0		0			0
Residential mortgage loans held for sale	0		0			0
Mortgage servicing rights	0		0			0
Derivative contracts, assets	0	[1]	0	[1]		16,991,000	[1]
Other assets - private equity funds	0		0			0
Impaired loans	0		0
Real Estate And Other Repossessed Assets	0		0
Liabilities [Abstract]
Certificates of deposit			0			0
Derivative contracts, liabilities	0		0			0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Assets [Abstract]
Trading securities	97,519,000		54,590,000			58,129,000
Available for sale securities [Abstract]
U.S. Treasury	0
Municipal and other tax-exempt	26,552,000		25,849,000			26,613,000
U.S. agency residential mortgage-backed securities	8,893,789,000		8,446,908,000			8,223,719,000
Private issue residential mortgage-backed securities	513,222,000		644,210,000			735,516,000
Other debt securities	0		1,000			29,000
Perpetual preferred stock	22,694,000		22,114,000			19,881,000
Equity securities and mutual funds	18,640,000		20,702,000			24,481,000
Total available for sale securities	9,474,897,000		9,159,784,000			9,030,239,000
Mortgage trading securities	553,231,000		428,021,000			534,641,000
Residential mortgage loans held for sale	169,609,000		263,413,000			227,574,000
Mortgage servicing rights	0		0			0
Derivative contracts, assets	229,887,000	[1]	270,445,000	[1]		317,585,000	[1]
Other assets - private equity funds	0		0			0
Impaired loans	17,949,000		55,893,000
Real Estate And Other Repossessed Assets	50,885,000		28,778,000
Liabilities [Abstract]
Certificates of deposit			27,414,000			27,957,000
Derivative contracts, liabilities	173,917,000		215,420,000			299,851,000
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Assets [Abstract]
Trading securities	0		0			0
Available for sale securities [Abstract]
U.S. Treasury	0
Municipal and other tax-exempt	43,658,000		47,093,000			39,826,000
U.S. agency residential mortgage-backed securities	0		0			0
Private issue residential mortgage-backed securities	0		0			0
Other debt securities	5,893,000		6,400,000			13,035,000
Perpetual preferred stock	0		0			0
Equity securities and mutual funds	0		0			0
Total available for sale securities	49,551,000		53,493,000			52,861,000
Mortgage trading securities	0		0			0
Residential mortgage loans held for sale	0		0			0
Mortgage servicing rights	109,192,000	[2]	115,723,000	[2]		98,984,000	[2]
Derivative contracts, assets	0	[1]	0	[1]		0	[1]
Other assets - private equity funds	28,313,000		25,436,000			23,834,000
Liabilities [Abstract]
Certificates of deposit			0			0
Derivative contracts, liabilities	0		0			0
Carrying (Reported) Amount, Fair Value Disclosure [Member]
Available for sale securities [Abstract]
U.S. Treasury	1,003,000
Municipal and other tax-exempt	70,210,000		72,942,000			66,439,000
U.S. agency residential mortgage-backed securities	8,893,789,000		8,446,908,000			8,223,719,000
Private issue residential mortgage-backed securities	513,222,000		644,210,000			735,516,000
Other debt securities	5,893,000		6,401,000			13,064,000
Perpetual preferred stock	22,694,000		22,114,000			19,881,000
Equity securities and mutual funds	60,197,000		43,046,000			47,209,000
Total available for sale securities	9,567,008,000		9,235,621,000			9,105,828,000
Mortgage trading securities	553,231,000		428,021,000			534,641,000
Residential mortgage loans held for sale	169,609,000		263,413,000			227,574,000
Mortgage servicing rights	109,192,000		115,723,000			98,942,000
Derivative contracts, assets	229,887,000		270,445,000			334,576,000
Other assets - private equity funds	28,313,000		25,436,000			23,834,000
Liabilities [Abstract]
Derivative contracts, liabilities	173,917,000		215,420,000			299,851,000
Estimate of Fair Value, Fair Value Disclosure [Member]
Available for sale securities [Abstract]
U.S. Treasury	1,003,000
Municipal and other tax-exempt	70,210,000		72,942,000			66,439,000
U.S. agency residential mortgage-backed securities	8,893,789,000		8,446,908,000			8,223,719,000
Private issue residential mortgage-backed securities	513,222,000		644,210,000			735,516,000
Other debt securities	5,893,000		6,401,000			13,064,000
Perpetual preferred stock	22,694,000		22,114,000			19,881,000
Equity securities and mutual funds	60,197,000		43,046,000			47,209,000
Total available for sale securities	9,567,008,000		9,235,621,000			9,105,828,000
Mortgage trading securities	553,231,000		428,021,000			534,641,000
Residential mortgage loans held for sale	169,609,000		263,413,000			227,574,000
Mortgage servicing rights	109,192,000		115,723,000			98,942,000
Derivative contracts, assets	229,887,000		270,445,000			334,576,000
Other assets - private equity funds	28,313,000		25,436,000			23,834,000
Liabilities [Abstract]
Derivative contracts, liabilities	$ 173,917,000		$ 215,420,000			$ 299,851,000

[1] See Note 3 for detail of fair value of derivative contracts by contract type.

[2] 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 5, Mortgage Banking Activities.