Derivatives (Narrative) (Details) MMBTU in Thousands, Boe in Thousands, $ in Thousands	3 Months Ended
Mar. 31, 2020 USD ($) MMBTU Boe company	Mar. 31, 2019 MMBTU Boe	Dec. 31, 2019 USD ($) company
Derivative [Line Items]
Derivative assets - Fair value	$ 834,204		$ 330,316
Derivative liabilities - Fair value	658,515		256,528
Credit-risk-related contingent features
Derivative [Line Items]
Aggregate fair value of derivative instruments in net liability position	139,100		56,400
Derivative asset			14,400
Derivative liability			70,800
Collateral posted	138,900		56,400
Derivative instruments designated as hedging instruments
Derivative [Line Items]
Notional amount	186,281		117,193
Derivative assets - Fair value	73		0
Derivative liabilities - Fair value	1,175		4,784
Derivative instruments designated as hedging instruments \| Foreign exchange contracts
Derivative [Line Items]
Notional amount	155,255		86,167
Derivative assets - Fair value	73		0
Derivative liabilities - Fair value	31		1,586
Derivative instruments designated as hedging instruments \| Interest rate contracts
Derivative [Line Items]
Notional amount	31,026		31,026
Derivative assets - Fair value	0		0
Derivative liabilities - Fair value	1,144		3,198
Derivatives not designated as hedging instruments
Derivative [Line Items]
Notional amount	21,826,497		20,540,031
Derivative assets - Fair value	834,131		330,316
Derivative liabilities - Fair value	657,340		251,744
Derivatives not designated as hedging instruments \| Foreign exchange contracts
Derivative [Line Items]
Notional amount	4,958,834		4,839,661
Derivative assets - Fair value	64,310		54,637
Derivative liabilities - Fair value	55,627		47,024
Derivatives not designated as hedging instruments \| Interest rate contracts
Derivative [Line Items]
Notional amount	16,657,306		15,489,692
Derivative assets - Fair value	605,122		192,883
Derivative liabilities - Fair value	402,207		124,119
Derivatives not designated as hedging instruments \| Interest rate contracts \| Financial Counterparty
Derivative [Line Items]
Notional amount	8,340,000		7,750,000
Derivatives not designated as hedging instruments \| Interest rate contracts \| LCH
Derivative [Line Items]
Notional amount	2,680,000		2,530,000
Derivative assets - Fair value			2,900
Derivative liabilities - Fair value	213,900		75,100
Derivatives not designated as hedging instruments \| Credit contracts
Derivative [Line Items]
Notional amount	210,357		210,678
Derivative assets - Fair value	8		2
Derivative liabilities - Fair value	$ 218		84
Weighted average remaining maturity of outstanding RPAs	1 year 10 months 24 days	2 years 2 months 12 days
Derivatives not designated as hedging instruments \| Credit contracts \| RPA protection sold
Derivative [Line Items]
Maximum exposure of RPAs with protection sold	$ 688		$ 125
Derivatives not designated as hedging instruments \| Equity, Public Companies
Derivative [Line Items]
Number of companies that issued the equity (issuers portion only) \| company	2		3
Derivatives not designated as hedging instruments \| Equity, Private Companies
Derivative [Line Items]
Number of companies that issued the equity (issuers portion only) \| company	18		18
Derivatives not designated as hedging instruments \| Equity contracts
Derivative [Line Items]
Notional amount	$ 0		$ 0
Derivative assets - Fair value	1,128		1,414
Derivative liabilities - Fair value	0		0
Derivatives not designated as hedging instruments \| Commodity contracts
Derivative [Line Items]
Notional amount	0		0
Derivative assets - Fair value	163,563		81,380
Derivative liabilities - Fair value	199,288		80,517
Derivatives not designated as hedging instruments \| Commodity contracts \| Chicago Mercantile Exchange (CME)
Derivative [Line Items]
Derivative assets - Fair value	39,600		2,900
Derivative liabilities - Fair value	203		1,500
Derivative assets (liabilities), at fair value, net	$ 2,400		986
Derivatives not designated as hedging instruments \| Commodity contracts \| Chicago Mercantile Exchange (CME) \| Oil
Derivative [Line Items]
Derivative, nonmonetary notional amount, energy measure \| Boe	1,582	1,752
Derivatives not designated as hedging instruments \| Commodity contracts \| Chicago Mercantile Exchange (CME) \| Natural gas
Derivative [Line Items]
Derivative, nonmonetary notional amount, energy measure \| MMBTU	5,290	6,075
Maximum \| Derivatives not designated as hedging instruments \| Foreign exchange contracts
Derivative [Line Items]
Original maturity (in years)	1 year	1 year
Derivative Financial Instruments, Assets \| Derivative instruments designated as hedging instruments \| Foreign exchange contracts
Derivative [Line Items]
Notional amount	$ 112,900
Derivative assets - Fair value	73
Derivative Financial Instruments, Liabilities \| Derivative instruments designated as hedging instruments \| Foreign exchange contracts
Derivative [Line Items]
Notional amount	42,300		86,200
Derivative liabilities - Fair value	$ 31		$ 1,600

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