Fair Value Measurements, Financial Instruments (Details) (USD $)	Sep. 30, 2013		Mar. 31, 2013	Dec. 31, 2012		Sep. 30, 2012		Mar. 31, 2012	Dec. 31, 2011
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	$ 150,887,000			$ 214,102,000		$ 204,242,000
Investment securities	644,225,000	[1]		499,534,000	[2]	432,114,000	[3]
Available for sale securities	10,372,903,000			11,287,221,000		11,506,434,000
Fair value option securities	167,860,000			284,296,000		331,887,000
Residential mortgage loans held for sale	230,511,000			293,762,000		325,102,000
Loans	12,350,100,000			12,311,456,000		11,832,367,000
Allowance for loan losses	(194,325,000)		(203,124,000)	(215,507,000)		(233,756,000)		(231,669,000)	(253,481,000)
Loans, net of allowance	12,155,775,000			12,095,949,000		11,598,611,000
Mortgage servicing rights	140,863,000		132,889,000	100,812,000		89,653,000		91,783,000	86,783,000
Derviative contracts, net of cash margin, assets	377,325,000			338,106,000		435,653,000
Time deposits	2,720,020,000			2,967,992,000		3,022,326,000
Subordinated debentures	347,758,000			347,633,000		347,592,000
Derivative contracts net of cash margin, liabilities	232,544,000			283,589,000		254,422,000
Fair Value Assumptions and Methodology for Assets and Liabilities [Abstract]
Specific allocation of allowance for loan losses included in fair value of loans	153,000,000			171,000,000		193,000,000
Commercial [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	7,571,075,000			7,641,912,000		7,266,907,000
Allowance for loan losses	(61,780,000)		(64,044,000)	(65,280,000)		(81,779,000)		(83,477,000)	(83,443,000)
Commercial Real Estate [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	2,349,229,000			2,228,999,000		2,177,272,000
Allowance for loan losses	(45,062,000)		(49,687,000)	(54,884,000)		(60,704,000)		(55,806,000)	(67,034,000)
Residential Mortgage [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	2,034,765,000			2,045,040,000		2,016,303,000
Allowance for loan losses	(38,297,000)		(39,206,000)	(41,703,000)		(41,016,000)		(42,688,000)	(46,476,000)
Consumer [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	395,031,000			395,505,000		371,885,000
Allowance for loan losses	(8,304,000)		(7,738,000)	(9,453,000)		(9,343,000)		(8,840,000)	(10,178,000)
U.S. Government agency debentures [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	74,632,000			16,545,000		3,100,000
U.S. agency residential mortgage-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	26,129,000			86,361,000		119,835,000
Available for sale securities	7,981,387,000			9,889,821,000		10,654,821,000
Fair value option securities	163,567,000			257,040,000		305,445,000
Municipal and other tax-exempt securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	37,057,000			90,326,000		58,150,000
Investment securities	409,542,000	[1]		232,700,000	[2]	155,144,000	[3]
Available for sale securities	95,440,000			87,142,000		87,969,000
Other trading securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	13,069,000			20,870,000		23,157,000
U.S. Treasury securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	1,052,000			1,002,000		1,002,000
Privately issued residential mortgage-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	230,900,000			325,163,000		331,722,000
Commercial mortgage-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	1,946,295,000			895,075,000		339,095,000
Other debt securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities	178,501,000	[1]		184,067,000	[2]	185,059,000	[3]
Available for sale securities	35,362,000			36,389,000		36,456,000
Fair value option securities	4,293,000			770,000		0
Perpetual preferred stock [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	23,680,000			25,072,000		25,288,000
Equity securities and mutual funds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	58,787,000			27,557,000		30,081,000
Corporate debt securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value option securities	0			26,486,000		26,442,000
Carrying (Reported) Amount, Fair Value Disclosure [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	1,133,771,000			1,286,239,000		615,494,000
Trading securities	150,887,000			214,102,000		204,242,000
Investment securities	644,225,000			499,534,000		432,114,000
Available for sale securities	10,372,903,000			11,287,221,000		11,506,434,000
Fair value option securities	167,860,000			284,296,000		331,887,000
Residential mortgage loans held for sale	230,511,000			293,762,000		325,102,000
Loans	12,350,100,000			12,311,456,000		11,832,367,000
Allowance for loan losses	(194,325,000)			215,507,000		233,756,000
Loans, net of allowance	12,155,775,000			12,095,949,000		11,598,611,000
Mortgage servicing rights	140,863,000			100,812,000		89,653,000
Derviative contracts, net of cash margin, assets	377,325,000			338,106,000		472,783,000
Other assets - private equity funds	27,799,000			28,169,000		28,791,000
Deposits with no stated maturity	16,771,635,000			18,211,068,000		16,120,541,000
Time deposits	2,720,020,000			2,967,992,000		3,022,326,000
Other borrowings	3,611,944,000			2,706,221,000		3,429,575,000
Subordinated debentures	347,758,000			347,633,000		347,592,000
Derivative contracts net of cash margin, liabilities	232,544,000			283,589,000		435,497,000
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Commercial [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	7,571,075,000			7,641,912,000		7,266,907,000
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Commercial Real Estate [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	2,349,229,000			2,228,999,000		2,177,272,000
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Residential Mortgage [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	2,034,765,000			2,045,040,000		2,016,303,000
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Consumer [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	395,031,000			395,505,000		371,885,000
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	74,632,000			16,545,000		3,100,000
Carrying (Reported) Amount, Fair Value Disclosure [Member] | U.S. agency residential mortgage-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	26,129,000			86,361,000		119,835,000
Investment securities	56,182,000			82,767,000		91,911,000
Available for sale securities	7,981,387,000			9,889,821,000		10,654,821,000
Fair value option securities	163,567,000			257,040,000		305,445,000
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	37,057,000			90,326,000		58,150,000
Investment securities	409,542,000			232,700,000		155,144,000
Available for sale securities	95,440,000			87,142,000		87,969,000
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Other trading securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	13,069,000			20,870,000		23,157,000
Carrying (Reported) Amount, Fair Value Disclosure [Member] | U.S. Treasury securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	1,052,000			1,002,000		1,002,000
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Privately issued residential mortgage-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	230,900,000			325,163,000		331,722,000
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Commercial mortgage-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	1,946,295,000			895,075,000		339,095,000
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Other debt securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities	178,501,000			184,067,000		185,059,000
Available for sale securities	35,362,000			36,389,000		36,456,000
Fair value option securities	4,293,000			770,000
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Perpetual preferred stock [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	23,680,000			25,072,000		25,288,000
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Equity securities and mutual funds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	58,787,000			27,557,000		30,081,000
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Corporate debt securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value option securities				26,486,000		26,442,000
Estimate of Fair Value, Fair Value Disclosure [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	1,133,771,000			1,286,239,000		615,494,000
Trading securities	150,887,000			214,102,000		204,242,000
Investment securities	654,479,000			528,458,000		460,358,000
Available for sale securities	10,372,903,000			11,287,221,000		11,506,434,000
Fair value option securities	167,860,000			284,296,000		331,887,000
Residential mortgage loans held for sale	230,511,000			293,762,000		325,102,000
Loans	12,264,613,000			12,314,243,000		11,827,797,000
Allowance for loan losses	0			0		0
Loans, net of allowance	12,264,613,000			12,314,243,000		11,827,797,000
Mortgage servicing rights	140,863,000			100,812,000		89,653,000
Derviative contracts, net of cash margin, assets	377,325,000			338,106,000		472,783,000
Other assets - private equity funds	27,799,000			28,169,000		28,791,000
Deposits with no stated maturity	16,771,635,000			18,211,068,000		16,120,541,000
Time deposits	2,739,764,000			3,037,708,000		3,099,183,000
Other borrowings	3,570,228,000			2,696,574,000		3,420,135,000
Subordinated debentures	344,854,000			345,675,000		345,852,000
Derivative contracts net of cash margin, liabilities	232,544,000			283,589,000		435,497,000
Estimate of Fair Value, Fair Value Disclosure [Member] | Commercial [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	7,493,143,000			7,606,505,000		7,232,761,000
Estimate of Fair Value, Fair Value Disclosure [Member] | Commercial Real Estate [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	2,326,908,000			2,208,217,000		2,142,239,000
Estimate of Fair Value, Fair Value Disclosure [Member] | Residential Mortgage [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	2,056,072,000			2,110,773,000		2,084,251,000
Estimate of Fair Value, Fair Value Disclosure [Member] | Consumer [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	388,490,000			388,748,000		368,546,000
Estimate of Fair Value, Fair Value Disclosure [Member] | U.S. Government agency debentures [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	74,632,000			16,545,000		3,100,000
Estimate of Fair Value, Fair Value Disclosure [Member] | U.S. agency residential mortgage-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	26,129,000			86,361,000		119,835,000
Investment securities	58,442,000			85,943,000		95,128,000
Available for sale securities	7,981,387,000			9,889,821,000		10,654,821,000
Fair value option securities	163,567,000			257,040,000		305,445,000
Estimate of Fair Value, Fair Value Disclosure [Member] | Municipal and other tax-exempt securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	37,057,000			90,326,000		58,150,000
Investment securities	407,562,000			235,940,000		159,464,000
Available for sale securities	95,440,000			87,142,000		87,969,000
Estimate of Fair Value, Fair Value Disclosure [Member] | Other trading securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	13,069,000			20,870,000		23,157,000
Estimate of Fair Value, Fair Value Disclosure [Member] | U.S. Treasury securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	1,052,000			1,002,000		1,002,000
Estimate of Fair Value, Fair Value Disclosure [Member] | Privately issued residential mortgage-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	230,900,000			325,163,000		331,722,000
Estimate of Fair Value, Fair Value Disclosure [Member] | Commercial mortgage-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	1,946,295,000			895,075,000		339,095,000
Estimate of Fair Value, Fair Value Disclosure [Member] | Other debt securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities	188,475,000			206,575,000		205,766,000
Available for sale securities	35,362,000			36,389,000		36,456,000
Fair value option securities	4,293,000			770,000
Estimate of Fair Value, Fair Value Disclosure [Member] | Perpetual preferred stock [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	23,680,000			25,072,000		25,288,000
Estimate of Fair Value, Fair Value Disclosure [Member] | Equity securities and mutual funds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	58,787,000			27,557,000		30,081,000
Estimate of Fair Value, Fair Value Disclosure [Member] | Corporate debt securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value option securities				26,486,000		26,442,000
Contractual Yield, Minimum [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Time deposits	0.0001			0.0001		0.0001
Other borrowings	0.0025			0.0009		0.0009
Subordinated debentures	0.0095			0.0100		0.0112
Contractual Yield, Minimum [Member] | Commercial [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	0.0025			0.0021		0.0025
Contractual Yield, Minimum [Member] | Commercial Real Estate [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	0.0038			0.0021		0.0038
Contractual Yield, Minimum [Member] | Residential Mortgage [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	0.0038			0.0038		0.0038
Contractual Yield, Minimum [Member] | Consumer [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	0.0038			0.0038		0.0038
Contractual Yield, Maximum [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Time deposits	0.0964			0.0964		0.0964
Other borrowings	0.0478			0.0525		0.0525
Subordinated debentures	0.0500			0.0500		0.0500
Contractual Yield, Maximum [Member] | Commercial [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	0.3000			0.3000		0.3000
Contractual Yield, Maximum [Member] | Commercial Real Estate [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	0.1800			0.1800		0.1800
Contractual Yield, Maximum [Member] | Residential Mortgage [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	0.1800			0.1800		0.1800
Contractual Yield, Maximum [Member] | Consumer [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	0.2100			0.2100		0.2100
Average Repricing [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Time deposits	2.08			2.15		2.14
Other borrowings	0.00			0.00		0.00
Subordinated debentures	2.87			3.56		3.79
Average Repricing [Member] | Commercial [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	0.46			0.69		0.64
Average Repricing [Member] | Commercial Real Estate [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	0.79			0.92		0.93
Average Repricing [Member] | Residential Mortgage [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	2.56			3.34		3.31
Average Repricing [Member] | Consumer [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	0.55			0.32		0.32
Discount Rate, Minimum [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Time deposits	0.0075			0.0080		0.0085
Other borrowings	0.0006			0.0009		0.0009
Subordinated debentures	0.0222			0.0240		0.0226
Discount Rate, Minimum [Member] | Commercial [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	0.0050			0.0051		0.0058
Discount Rate, Minimum [Member] | Commercial Real Estate [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	0.0120			0.0126		0.0130
Discount Rate, Minimum [Member] | Residential Mortgage [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	0.0064			0.0086		0.0099
Discount Rate, Minimum [Member] | Consumer [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	0.0124			0.0137		0.0143
Discount Rate, Maximum [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Time deposits	0.0128			0.0115		0.0115
Other borrowings	0.0265			0.0267		0.0267
Subordinated debentures	0.0222			0.0240		0.0226
Discount Rate, Maximum [Member] | Commercial [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	0.0419			0.0359		0.0350
Discount Rate, Maximum [Member] | Commercial Real Estate [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	0.0342			0.0318		0.0317
Discount Rate, Maximum [Member] | Residential Mortgage [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	0.0440			0.0309		0.0317
Discount Rate, Maximum [Member] | Consumer [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	$ 0.0371			$ 0.0360		$ 0.0369

[1] Carrying value includes $2.3 million of net unrealized gain which remains in Accumulated other comprehensive income (“AOCI”) in the Consolidated Balance Sheets related to certain securities transferred from the Available for Sale securities portfolio to the Investment securities portfolio as discussed in greater detail following.

[2] Carrying value includes $5.0 million of net unrealized gain which remains in Accumulated other comprehensive income (“AOCI”) in the Consolidated Balance Sheets related to certain securities transferred from the Available for Sale securities portfolio to the Investment securities portfolio as discussed in greater detail following.

[3] Carrying value includes $6.2 million of net unrealized gain which remains in Accumulated other comprehensive income (“AOCI”) in the Consolidated Balance Sheets related to certain securities transferred from the Available for Sale securities portfolio to the Investment securities portfolio as discussed in greater detail following.