Derivatives (Narrative) (Details) MMBTU in Thousands, Boe in Thousands, $ in Thousands	6 Months Ended	12 Months Ended
Jun. 30, 2020 USD ($) Boe MMBTU company	Dec. 31, 2019 USD ($) MMBTU Boe company
Derivative [Line Items]
Derivative assets - Fair value	$ 764,430	$ 330,316
Derivative liabilities - Fair value	560,169	256,528
Credit-risk-related contingent features
Derivative [Line Items]
Aggregate fair value of derivative instruments in net liability position	136,600	56,400
Derivative asset		14,400
Derivative liability		70,800
Collateral posted	136,500	56,400
Derivative instruments designated as hedging instruments
Derivative [Line Items]
Notional amount	367,883	117,193
Derivative assets - Fair value	245	0
Derivative liabilities - Fair value	1,657	4,784
Derivative instruments designated as hedging instruments \| Interest rate contracts \| Cash Flow Hedging
Derivative [Line Items]
Notional amount	275,000	0
Net unrealized gains, net of tax, recorded in AOCI expected to be reclassified into earnings during next 12 months	183
Derivative assets - Fair value	0	0
Derivative liabilities - Fair value	1,483	0
Derivatives not designated as hedging instruments
Derivative [Line Items]
Notional amount	20,113,400	20,540,031
Derivative assets - Fair value	764,185	330,316
Derivative liabilities - Fair value	558,512	251,744
Derivatives not designated as hedging instruments \| Foreign exchange contracts
Derivative [Line Items]
Notional amount	2,738,018	4,839,661
Derivative assets - Fair value	24,044	54,637
Derivative liabilities - Fair value	19,741	47,024
Derivatives not designated as hedging instruments \| Interest rate contracts
Derivative [Line Items]
Notional amount	17,170,884	15,489,692
Derivative assets - Fair value	613,480	192,883
Derivative liabilities - Fair value	400,146	124,119
Derivatives not designated as hedging instruments \| Interest rate contracts \| Financial Counterparty
Derivative [Line Items]
Notional amount	8,600,000	7,750,000
Derivatives not designated as hedging instruments \| Interest rate contracts \| LCH
Derivative [Line Items]
Notional amount	2,820,000	2,530,000
Derivative assets - Fair value		2,900
Derivative liabilities - Fair value	229,800	75,100
Derivatives not designated as hedging instruments \| Credit contracts
Derivative [Line Items]
Notional amount	204,498	210,678
Derivative assets - Fair value	41	2
Derivative liabilities - Fair value	$ 327	$ 84
Weighted average remaining maturity of outstanding RPAs	1 year 8 months 12 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	$ 778	$ 125
Derivatives not designated as hedging instruments \| Equity, Public Companies
Derivative [Line Items]
Number of companies that issued the equity (issuers portion only) \| company	3	3
Derivatives not designated as hedging instruments \| Equity contracts
Derivative [Line Items]
Notional amount	$ 0	$ 0
Derivative assets - Fair value	9,173	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	117,447	81,380
Derivative liabilities - Fair value	138,298	80,517
Derivatives not designated as hedging instruments \| Commodity contracts \| Chicago Mercantile Exchange (CME)
Derivative [Line Items]
Derivative assets - Fair value	25,000	2,900
Derivative liabilities - Fair value	631	1,500
Derivative assets (liabilities), at fair value, net	$ 2,300	$ 986
Derivatives not designated as hedging instruments \| Commodity contracts \| Chicago Mercantile Exchange (CME) \| Oil
Derivative [Line Items]
Derivative, nonmonetary notional amount, energy measure \| Boe	1,532	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	24,895	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]
Derivative assets - Fair value	$ 245
Derivative Financial Instruments, Liabilities \| Derivative instruments designated as hedging instruments \| Foreign exchange contracts
Derivative [Line Items]
Notional amount	$ 77,700	$ 86,200
Derivative liabilities - Fair value		$ 1,600

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