Derivatives (Notional and Fair Values) (Details) MMBTU in Thousands, Boe in Thousands, $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2021 USD ($) Boe MMBTU company	Dec. 31, 2020 USD ($) Boe MMBTU company
Derivative Asset [Abstract]
Derivative assets - Fair value	$ 694,010	$ 602,754
Less: Master netting agreements	(102,515)	(93,063)
Less: Cash collateral received/paid	(62,968)	(8,449)
Net derivative assets	528,527	501,242
Derivative Liability [Abstract]
Derivative liabilities - Fair value	561,788	424,828
Less: Master netting agreements	(102,515)	(93,063)
Less: Cash collateral received/paid	(240,104)	(91,634)
Net derivative liabilities	$ 219,169	$ 240,131
Crude oil \| Customer Counterparty
Derivative Liability [Abstract]
Derivative, nonmonetary notional amount, energy measure \| Boe	8,557	6,321
Natural gas \| Customer Counterparty
Derivative Liability [Abstract]
Derivative, nonmonetary notional amount, energy measure \| MMBTU	95,273	109,635
Derivative instruments designated as hedging instruments
Derivative Instruments
Notional Amount	$ 360,316	$ 359,269
Derivative Asset [Abstract]
Derivative assets - Fair value	158	0
Derivative Liability [Abstract]
Derivative liabilities - Fair value	1,149	2,099
Derivative instruments designated as hedging instruments \| Cash Flow Hedging \| Interest rate contracts
Derivative Instruments
Notional Amount	275,000	275,000
Derivative Asset [Abstract]
Derivative assets - Fair value	0	0
Derivative Liability [Abstract]
Derivative liabilities - Fair value	1,149	1,864
Derivative instruments designated as hedging instruments \| Net Investment Hedging \| Foreign exchange contracts
Derivative Instruments
Notional Amount	85,316	84,269
Derivative Asset [Abstract]
Derivative assets - Fair value	158	0
Derivative Liability [Abstract]
Derivative liabilities - Fair value	0	235
Derivatives not designated as hedging instruments
Derivative Instruments
Notional Amount	20,874,985	21,341,158
Derivative Asset [Abstract]
Derivative assets - Fair value	693,852	602,754
Derivative Liability [Abstract]
Derivative liabilities - Fair value	560,639	422,729
Derivatives not designated as hedging instruments \| Interest rate contracts
Derivative Instruments
Notional Amount	17,743,446	18,155,678
Derivative Asset [Abstract]
Derivative assets - Fair value	298,831	489,132
Derivative Liability [Abstract]
Derivative liabilities - Fair value	212,179	315,834
Derivatives not designated as hedging instruments \| Foreign exchange contracts
Derivative Instruments
Notional Amount	3,047,846	3,108,488
Derivative Asset [Abstract]
Derivative assets - Fair value	31,717	30,300
Derivative Liability [Abstract]
Derivative liabilities - Fair value	24,313	22,524
Derivatives not designated as hedging instruments \| Credit contracts
Derivative Instruments
Notional Amount	83,693	76,992
Derivative Asset [Abstract]
Derivative assets - Fair value	15	13
Derivative Liability [Abstract]
Derivative liabilities - Fair value	120	206
Derivatives not designated as hedging instruments \| Equity contracts
Derivative Instruments
Notional Amount	0	0
Derivative Asset [Abstract]
Derivative assets - Fair value	226	858
Derivative Liability [Abstract]
Derivative liabilities - Fair value	0	0
Derivatives not designated as hedging instruments \| Commodity contracts
Derivative Instruments
Notional Amount	0	0
Derivative Asset [Abstract]
Derivative assets - Fair value	363,063	82,451
Derivative Liability [Abstract]
Derivative liabilities - Fair value	$ 324,027	$ 84,165
Derivatives not designated as hedging instruments \| Equity, Public Companies
Derivative Liability [Abstract]
Number of companies that issued the equity (issuers portion only) \| company	1	2
Derivatives not designated as hedging instruments \| Equity, Private Companies
Derivative Liability [Abstract]
Number of companies that issued the equity (issuers portion only) \| company	12	17

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