Derivatives, Fair Value of Derivatives Contracts (Details) - USD ($) $ in Thousands	Jun. 30, 2017		Dec. 31, 2016		Jun. 30, 2016
Derivative Assets, Fair Value, Net [Abstract]
Derviative contracts, net of cash collateral, Assets, Fair value	$ 280,289		$ 689,872		$ 883,673
Derivative Liabilities, Fair Value, Net [Abstract]
Derivative Liabilities, Fair Value, Net of Cash Collateral	285,819		664,531		719,159
Not Designated as Hedging Instrument [Member]
Notional Amount of Derivatives [Abstract]
Derivative Assets, Notional	29,511,796	[1]	22,437,314	[2]	23,037,973	[3]
Derivative Liabilities, Notional	27,125,429	[1]	22,178,359	[2]	21,565,820	[3]
Derivative Assets, Fair Value, Net [Abstract]
Derivative Assets, Gross Fair Value	355,296		789,791		993,485
Derivative Assets, Netting Adjustments	(50,607)		(89,368)		(102,988)
Derivative Assets, Net Fair Value Before Cash Collateral	304,689		700,423		890,497
Derivative Assets, Cash Collateral	(24,400)		(10,551)		(6,824)
Derviative contracts, net of cash collateral, Assets, Fair value	280,289		689,872		883,673
Derivative Liabilities, Fair Value, Net [Abstract]
Derivative Liabilities, Gross Fair Value	357,521		801,809		974,975
Derivative Liabilities, Netting Adjustments	(50,607)		(89,368)		(102,988)
Derivative Liabilities, Net Fair Value Before Cash Collateral	306,914		712,441		871,987
Derivative Liabilities, Cash Collateral	(21,095)		(47,910)		(152,828)
Derivative Liabilities, Fair Value, Net of Cash Collateral	285,819		664,531		719,159
Not Designated as Hedging Instrument [Member] | To-be-announced residential mortgage-backed securities
Notional Amount of Derivatives [Abstract]
Derivative Assets, Notional	16,174,687	[1]	16,949,152	[2]	18,774,134	[3]
Derivative Liabilities, Notional	16,174,687	[1]	16,637,532	[2]	18,662,334	[3]
Derivative Assets, Fair Value, Net [Abstract]
Derivative Assets, Gross Fair Value	57,948		180,695		183,118
Derivative Assets, Netting Adjustments	(29,034)		(60,555)		(67,383)
Derivative Assets, Net Fair Value Before Cash Collateral	28,914		120,140		115,735
Derivative Assets, Cash Collateral	0		0		0
Derviative contracts, net of cash collateral, Assets, Fair value	28,914		120,140		115,735
Derivative Liabilities, Fair Value, Net [Abstract]
Derivative Liabilities, Gross Fair Value	53,829		176,928		179,443
Derivative Liabilities, Netting Adjustments	(29,034)		(60,555)		(67,383)
Derivative Liabilities, Net Fair Value Before Cash Collateral	24,795		116,373		112,060
Derivative Liabilities, Cash Collateral	0		0		(103,724)
Derivative Liabilities, Fair Value, Net of Cash Collateral	24,795		116,373		8,336
Not Designated as Hedging Instrument [Member] | Interest rate swaps
Notional Amount of Derivatives [Abstract]
Derivative Assets, Notional	1,450,193	[1]	1,403,408	[2]	1,299,985	[3]
Derivative Liabilities, Notional	1,450,193	[1]	1,403,408	[2]	1,299,985	[3]
Derivative Assets, Fair Value, Net [Abstract]
Derivative Assets, Gross Fair Value	29,932		34,442		54,978
Derivative Assets, Netting Adjustments	0		0		0
Derivative Assets, Net Fair Value Before Cash Collateral	29,932		34,442		54,978
Derivative Assets, Cash Collateral	(2,206)		(4,567)		(1,100)
Derviative contracts, net of cash collateral, Assets, Fair value	27,726		29,875		53,878
Derivative Liabilities, Fair Value, Net [Abstract]
Derivative Liabilities, Gross Fair Value	29,982		34,442		55,404
Derivative Liabilities, Netting Adjustments	0		0		0
Derivative Liabilities, Net Fair Value Before Cash Collateral	29,982		34,442		55,404
Derivative Liabilities, Cash Collateral	(15,396)		(11,977)		(32,597)
Derivative Liabilities, Fair Value, Net of Cash Collateral	14,586		22,465		22,807
Not Designated as Hedging Instrument [Member] | Energy contracts
Notional Amount of Derivatives [Abstract]
Derivative Assets, Notional	891,480	[1]	835,566	[2]	757,669	[3]
Derivative Liabilities, Notional	874,625	[1]	820,365	[2]	734,538	[3]
Derivative Assets, Fair Value, Net [Abstract]
Derivative Assets, Gross Fair Value	56,824		64,140		59,103
Derivative Assets, Netting Adjustments	(20,546)		(28,298)		(33,996)
Derivative Assets, Net Fair Value Before Cash Collateral	36,278		35,842		25,107
Derivative Assets, Cash Collateral	(21,267)		(71)		(155)
Derviative contracts, net of cash collateral, Assets, Fair value	15,011		35,771		24,952
Derivative Liabilities, Fair Value, Net [Abstract]
Derivative Liabilities, Gross Fair Value	53,895		64,306		58,033
Derivative Liabilities, Netting Adjustments	(20,546)		(28,298)		(33,996)
Derivative Liabilities, Net Fair Value Before Cash Collateral	33,349		36,008		24,037
Derivative Liabilities, Cash Collateral	0		(31,534)		(11,784)
Derivative Liabilities, Fair Value, Net of Cash Collateral	33,349		4,474		12,253
Not Designated as Hedging Instrument [Member] | Agricultural contracts
Notional Amount of Derivatives [Abstract]
Derivative Assets, Notional	45,250	[1]	53,209	[2]	50,848	[3]
Derivative Liabilities, Notional	45,262	[1]	53,216	[2]	50,843	[3]
Derivative Assets, Fair Value, Net [Abstract]
Derivative Assets, Gross Fair Value	3,541		1,382		2,488
Derivative Assets, Netting Adjustments	(1,027)		(515)		(1,609)
Derivative Assets, Net Fair Value Before Cash Collateral	2,514		867		879
Derivative Assets, Cash Collateral	0		0		(37)
Derviative contracts, net of cash collateral, Assets, Fair value	2,514		867		842
Derivative Liabilities, Fair Value, Net [Abstract]
Derivative Liabilities, Gross Fair Value	3,538		1,365		2,476
Derivative Liabilities, Netting Adjustments	(1,027)		(515)		(1,609)
Derivative Liabilities, Net Fair Value Before Cash Collateral	2,511		850		867
Derivative Liabilities, Cash Collateral	(2,511)		(769)		0
Derivative Liabilities, Fair Value, Net of Cash Collateral	0		81		867
Not Designated as Hedging Instrument [Member] | Foreign exchange contracts
Notional Amount of Derivatives [Abstract]
Derivative Assets, Notional	169,529	[1]	580,886	[2]	701,436	[3]
Derivative Liabilities, Notional	169,553	[1]	580,712	[2]	701,219	[3]
Derivative Assets, Fair Value, Net [Abstract]
Derivative Assets, Gross Fair Value	162,429		494,349		675,804
Derivative Assets, Netting Adjustments	0		0		0
Derivative Assets, Net Fair Value Before Cash Collateral	162,429		494,349		675,804
Derivative Assets, Cash Collateral	(7)		(5,183)		(5,054)
Derviative contracts, net of cash collateral, Assets, Fair value	162,422		489,166		670,750
Derivative Liabilities, Fair Value, Net [Abstract]
Derivative Liabilities, Gross Fair Value	162,276		494,695		675,383
Derivative Liabilities, Netting Adjustments	0		0		0
Derivative Liabilities, Net Fair Value Before Cash Collateral	162,276		494,695		675,383
Derivative Liabilities, Cash Collateral	(3,188)		(3,630)		(4,723)
Derivative Liabilities, Fair Value, Net of Cash Collateral	159,088		491,065		670,660
Not Designated as Hedging Instrument [Member] | Equity option contracts
Notional Amount of Derivatives [Abstract]
Derivative Assets, Notional	100,159	[1]	100,924	[2]	116,901	[3]
Derivative Liabilities, Notional	100,159	[1]	100,924	[2]	116,901	[3]
Derivative Assets, Fair Value, Net [Abstract]
Derivative Assets, Gross Fair Value	4,437		4,357		4,236
Derivative Assets, Netting Adjustments	0		0		0
Derivative Assets, Net Fair Value Before Cash Collateral	4,437		4,357		4,236
Derivative Assets, Cash Collateral	(920)		(730)		(478)
Derviative contracts, net of cash collateral, Assets, Fair value	3,517		3,627		3,758
Derivative Liabilities, Fair Value, Net [Abstract]
Derivative Liabilities, Gross Fair Value	4,437		4,357		4,236
Derivative Liabilities, Netting Adjustments	0		0		0
Derivative Liabilities, Net Fair Value Before Cash Collateral	4,437		4,357		4,236
Derivative Liabilities, Cash Collateral	0		0		0
Derivative Liabilities, Fair Value, Net of Cash Collateral	4,437		4,357		4,236
Not Designated as Hedging Instrument [Member] | Total customer risk management programs
Notional Amount of Derivatives [Abstract]
Derivative Assets, Notional	18,831,298	[1]	19,923,145	[2]	21,700,973	[3]
Derivative Liabilities, Notional	18,814,479	[1]	19,596,157	[2]	21,565,820	[3]
Derivative Assets, Fair Value, Net [Abstract]
Derivative Assets, Gross Fair Value	315,111		779,365		979,727
Derivative Assets, Netting Adjustments	(50,607)		(89,368)		(102,988)
Derivative Assets, Net Fair Value Before Cash Collateral	264,504		689,997		876,739
Derivative Assets, Cash Collateral	(24,400)		(10,551)		(6,824)
Derviative contracts, net of cash collateral, Assets, Fair value	240,104		679,446		869,915
Derivative Liabilities, Fair Value, Net [Abstract]
Derivative Liabilities, Gross Fair Value	307,957		776,093		974,975
Derivative Liabilities, Netting Adjustments	(50,607)		(89,368)		(102,988)
Derivative Liabilities, Net Fair Value Before Cash Collateral	257,350		686,725		871,987
Derivative Liabilities, Cash Collateral	(21,095)		(47,910)		(152,828)
Derivative Liabilities, Fair Value, Net of Cash Collateral	236,255		638,815		719,159
Not Designated as Hedging Instrument [Member] | Internal risk management programs
Notional Amount of Derivatives [Abstract]
Derivative Assets, Notional	10,680,498	[1]	2,514,169	[2]	1,337,000	[3]
Derivative Liabilities, Notional	8,310,950	[1]	2,582,202	[2]	0	[3]
Derivative Assets, Fair Value, Net [Abstract]
Derivative Assets, Gross Fair Value	40,185		10,426		13,758
Derivative Assets, Netting Adjustments	0		0		0
Derivative Assets, Net Fair Value Before Cash Collateral	40,185		10,426		13,758
Derivative Assets, Cash Collateral	0		0		0
Derviative contracts, net of cash collateral, Assets, Fair value	40,185		10,426		13,758
Derivative Liabilities, Fair Value, Net [Abstract]
Derivative Liabilities, Gross Fair Value	49,564		25,716		0
Derivative Liabilities, Netting Adjustments	0		0		0
Derivative Liabilities, Net Fair Value Before Cash Collateral	49,564		25,716		0
Derivative Liabilities, Cash Collateral	0		0		0
Derivative Liabilities, Fair Value, Net of Cash Collateral	$ 49,564		$ 25,716		$ 0

[1] Notional amounts for commodity contracts are converted into dollar-equivalent amounts based on dollar prices at the inception of the contract.

[2] Notional amounts for commodity contracts are converted into dollar-equivalent amounts based on dollar prices at the inception of the contract.

[3] Notional amounts for commodity contracts are converted into dollar-equivalent amounts based on dollar prices at the inception of the contract.