Fair Value Measurements, Fair Value Of Financial Instruments as Measured On a Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2015		Dec. 31, 2014		Dec. 31, 2013	Dec. 31, 2012
Assets [Abstract]
Trading securities	$ 122,404		$ 188,700
Available for sale securities	9,042,733		8,978,945
Fair value option securities	444,217		311,597
Mortgage servicing rights	218,605		171,976		$ 153,333	$ 100,812
Derivative contracts, net of cash margin, Assets, Fair Value	586,270		361,874
Liabilities [Abstract]
Derivative contracts, net of cash margin, Liabilities, Fair Value	581,701		354,554
U.S. government agency debentures [Member]
Assets [Abstract]
Trading securities	61,295		85,092
U.S. government agency residential mortgage-backed securities [Member]
Assets [Abstract]
Trading securities	10,989		31,199
Available for sale securities	5,898,351		6,646,884
Fair value option securities	444,217		311,597
Municipal and other tax-exempt securities [Member]
Assets [Abstract]
Trading securities	31,901		38,951
Available for sale securities	56,817		63,557
Other trading securities [Member]
Assets [Abstract]
Trading securities	18,219		33,458
U.S. Treasury securities [Member]
Assets [Abstract]
Available for sale securities	995		1,005
Privately issued residential mortgage-backed securities [Member]
Assets [Abstract]
Available for sale securities	139,118		165,957
Commercial mortgage-backed securities guaranteed by U.S. government agencies [Member]
Assets [Abstract]
Available for sale securities	2,905,796		2,048,609
Other debt securities [Member]
Assets [Abstract]
Available for sale securities	4,151		9,212
Perpetual preferred stock [Member]
Assets [Abstract]
Available for sale securities	19,672		24,277
Equity securities and mutual funds [Member]
Assets [Abstract]
Available for sale securities	17,833		19,444
Fair Value, Measurements, Recurring [Member]
Assets [Abstract]
Trading securities	122,404		188,700
Available for sale securities	9,042,733		8,978,945
Residential mortgage loans held for sale	308,439		304,182
Mortgage servicing rights	218,605	[1]	171,976	[2]
Derivative contracts, net of cash margin, Assets, Fair Value	586,270	[3]	361,874	[4]
Other assets, private equity funds	22,472		25,627
Liabilities [Abstract]
Derivative contracts, net of cash margin, Liabilities, Fair Value	581,701	[3]	354,554	[4]
Fair Value, Measurements, Recurring [Member] | U.S. government agency debentures [Member]
Assets [Abstract]
Trading securities	61,295		85,092
Fair Value, Measurements, Recurring [Member] | U.S. government agency residential mortgage-backed securities [Member]
Assets [Abstract]
Trading securities	10,989		31,199
Available for sale securities	5,898,351		6,646,884
Fair value option securities	444,217		311,597
Fair Value, Measurements, Recurring [Member] | Municipal and other tax-exempt securities [Member]
Assets [Abstract]
Trading securities	31,901		38,951
Available for sale securities	56,817		63,557
Fair Value, Measurements, Recurring [Member] | Other trading securities [Member]
Assets [Abstract]
Trading securities	18,219		33,458
Fair Value, Measurements, Recurring [Member] | U.S. Treasury securities [Member]
Assets [Abstract]
Available for sale securities	995		1,005
Fair Value, Measurements, Recurring [Member] | Privately issued residential mortgage-backed securities [Member]
Assets [Abstract]
Available for sale securities	139,118		165,957
Fair Value, Measurements, Recurring [Member] | Commercial mortgage-backed securities guaranteed by U.S. government agencies [Member]
Assets [Abstract]
Available for sale securities	2,905,796		2,048,609
Fair Value, Measurements, Recurring [Member] | Other debt securities [Member]
Assets [Abstract]
Available for sale securities	4,151		9,212
Fair Value, Measurements, Recurring [Member] | Perpetual preferred stock [Member]
Assets [Abstract]
Available for sale securities	19,672		24,277
Fair Value, Measurements, Recurring [Member] | Equity securities and mutual funds [Member]
Assets [Abstract]
Available for sale securities	17,833		19,444
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Assets [Abstract]
Trading securities	0		0
Available for sale securities	4,260		5,932
Residential mortgage loans held for sale	0		0
Mortgage servicing rights	0	[1]	0	[2]
Derivative contracts, net of cash margin, Assets, Fair Value	38,530	[3]	17,607	[4]
Other assets, private equity funds	0		0
Liabilities [Abstract]
Derivative contracts, net of cash margin, Liabilities, Fair Value	0	[3]	541	[4]
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | U.S. government agency debentures [Member]
Assets [Abstract]
Trading securities	0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | U.S. government agency residential mortgage-backed securities [Member]
Assets [Abstract]
Trading securities	0		0
Available for sale securities	0		0
Fair value option securities	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
Available for sale securities	0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Other trading securities [Member]
Assets [Abstract]
Trading securities	0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | U.S. Treasury securities [Member]
Assets [Abstract]
Available for sale securities	995		1,005
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
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
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Other debt securities [Member]
Assets [Abstract]
Available for sale securities	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
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Equity securities and mutual funds [Member]
Assets [Abstract]
Available for sale securities	3,265		4,927
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Assets [Abstract]
Trading securities	122,404		188,700
Available for sale securities	9,024,712		8,958,770
Residential mortgage loans held for sale	300,565		292,326
Mortgage servicing rights	0	[1]	0	[2]
Derivative contracts, net of cash margin, Assets, Fair Value	547,740	[3]	344,267	[4]
Other assets, private equity funds	0		0
Liabilities [Abstract]
Derivative contracts, net of cash margin, Liabilities, Fair Value	581,701	[3]	354,013	[4]
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | U.S. government agency debentures [Member]
Assets [Abstract]
Trading securities	61,295		85,092
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | U.S. government agency residential mortgage-backed securities [Member]
Assets [Abstract]
Trading securities	10,989		31,199
Available for sale securities	5,898,351		6,646,884
Fair value option securities	444,217		311,597
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Municipal and other tax-exempt securities [Member]
Assets [Abstract]
Trading securities	31,901		38,951
Available for sale securities	47,207		53,464
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Other trading securities [Member]
Assets [Abstract]
Trading securities	18,219		33,458
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | U.S. Treasury securities [Member]
Assets [Abstract]
Available for sale securities	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	139,118		165,957
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	2,905,796		2,048,609
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Other debt securities [Member]
Assets [Abstract]
Available for sale securities	0		5,062
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Perpetual preferred stock [Member]
Assets [Abstract]
Available for sale securities	19,672		24,277
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Equity securities and mutual funds [Member]
Assets [Abstract]
Available for sale securities	14,568		14,517
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Assets [Abstract]
Trading securities	0		0
Available for sale securities	13,761		14,243
Residential mortgage loans held for sale	7,874		11,856
Mortgage servicing rights	218,605	[1]	171,976	[2]
Derivative contracts, net of cash margin, Assets, Fair Value	0	[3]	0	[4]
Other assets, private equity funds	22,472		25,627
Liabilities [Abstract]
Derivative contracts, net of cash margin, Liabilities, Fair Value	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
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | U.S. government agency residential mortgage-backed securities [Member]
Assets [Abstract]
Trading securities	0		0
Available for sale securities	0		0
Fair value option securities	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
Available for sale securities	9,610		10,093
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Other trading securities [Member]
Assets [Abstract]
Trading securities	0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | U.S. Treasury securities [Member]
Assets [Abstract]
Available for sale securities	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
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
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Other debt securities [Member]
Assets [Abstract]
Available for sale securities	4,151		4,150
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Perpetual preferred stock [Member]
Assets [Abstract]
Available for sale securities	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		$ 0

[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 7, Mortgage Banking Activities.

[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 7, Mortgage Banking Activities.

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

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