Derivatives (Narrative) (Details) MMBTU in Thousands, Boe in Thousands, $ in Thousands	12 Months Ended
Dec. 31, 2019 USD ($) MMBTU Boe company	Dec. 31, 2018 USD ($) MMBTU Boe company
Derivative [Line Items]
Derivative liabilities - Fair Value	$ 256,528	$ 118,305
Derivative assets - Fair value	330,316	107,816
Credit-Risk-Related Contingent Features
Derivative [Line Items]
Derivative asset	14,400	2,800
Derivative liability	70,800	14,200
Associated posted collateral	56,400	9,400
Aggregate fair value of derivative instruments in net liability position	56,400	11,400
Derivative instruments designated as hedging instruments
Derivative [Line Items]
Notional amount	117,193	126,056
Derivative liabilities - Fair Value	4,784	6,477
Derivative assets - Fair value	0	0
Derivative instruments designated as hedging instruments \| Foreign exchange contracts
Derivative [Line Items]
Notional amount	86,167	90,245
Derivative liabilities - Fair Value	1,586	611
Derivative assets - Fair value	0	0
Derivative instruments designated as hedging instruments \| Interest rate contracts
Derivative [Line Items]
Notional amount	31,026	35,811
Derivative liabilities - Fair Value	3,198	5,866
Derivative assets - Fair value	0	0
Derivative instruments not designated as hedging instruments
Derivative [Line Items]
Notional amount	20,540,031	15,222,341
Derivative liabilities - Fair Value	251,744	111,828
Derivative assets - Fair value	330,316	107,816
Derivative instruments not designated as hedging instruments \| Foreign exchange contracts
Derivative [Line Items]
Notional amount	4,839,661	3,407,522
Derivative liabilities - Fair Value	47,024	19,329
Derivative assets - Fair value	54,637	21,624
Derivative instruments not designated as hedging instruments \| Interest rate contracts
Derivative [Line Items]
Notional amount	15,489,692	11,695,499
Derivative liabilities - Fair Value	124,119	69,267
Derivative assets - Fair value	192,883	69,818
Derivative instruments not designated as hedging instruments \| Credit contracts
Derivative [Line Items]
Notional amount	210,678	119,320
Derivative liabilities - Fair Value	84	164
Derivative assets - Fair value	$ 2	$ 1
Weighted average remaining maturity	2 years 2 months 12 days	6 years 7 months 6 days
Derivative instruments not designated as hedging instruments \| Credit contracts \| RPAs - protection sold
Derivative [Line Items]
Maximum exposure of RPAs with protection sold	$ 125	$ 125
Derivative instruments not designated as hedging instruments \| Equity, Private Companies
Derivative [Line Items]
Number of companies that Issued the equity contracts (Issuers Portion Only) \| company	18	18
Derivative instruments not designated as hedging instruments \| Equity, Public Companies
Derivative [Line Items]
Number of companies that Issued the equity contracts (Issuers Portion Only) \| company	3	4
Derivative instruments not designated as hedging instruments \| Equity warrants
Derivative [Line Items]
Notional amount	$ 0	$ 0
Derivative liabilities - Fair Value	0	0
Derivative assets - Fair value	1,414	1,951
Derivative instruments not designated as hedging instruments \| Commodity contracts
Derivative [Line Items]
Notional amount	0	0
Derivative liabilities - Fair Value	80,517	23,068
Derivative assets - Fair value	81,380	14,422
Fair Value, Measurements, Recurring
Derivative [Line Items]
Derivative liabilities - Fair Value	256,528	118,305
Derivative assets - Fair value	330,316	107,816
Fair Value, Measurements, Recurring \| Foreign exchange contracts
Derivative [Line Items]
Derivative liabilities - Fair Value	48,610	19,940
Derivative assets - Fair value	54,637	21,624
Fair Value, Measurements, Recurring \| Interest rate contracts
Derivative [Line Items]
Derivative liabilities - Fair Value	127,317	75,133
Derivative assets - Fair value	192,883	69,818
Fair Value, Measurements, Recurring \| Credit contracts
Derivative [Line Items]
Derivative liabilities - Fair Value	84	164
Derivative assets - Fair value	2	1
Fair Value, Measurements, Recurring \| Equity warrants
Derivative [Line Items]
Derivative assets - Fair value	1,414	1,951
Fair Value, Measurements, Recurring \| Commodity contracts
Derivative [Line Items]
Derivative liabilities - Fair Value	80,517	23,068
Derivative assets - Fair value	81,380	14,422
Financial Counterparty \| Derivative instruments not designated as hedging instruments \| Interest rate contracts
Derivative [Line Items]
Notional amount	7,750,000	5,850,000
London Clearing House \| Derivative instruments not designated as hedging instruments \| Interest rate contracts
Derivative [Line Items]
Notional amount	2,530,000	1,660,000
Derivative liabilities - Fair Value	75,100	16,000
Derivative assets - Fair value	2,900	16,400
Chicago Mercantile Exchange (CME) \| Derivative instruments not designated as hedging instruments \| Commodity contracts
Derivative [Line Items]
Derivative liabilities - Fair Value		582
Derivative assets - Fair value	2,900	10,400
Derivative liability	1,500
Derivative assets (liabilities), at fair value	$ 986	$ 622
Chicago Mercantile Exchange (CME) \| Derivative instruments not designated as hedging instruments \| Commodity contracts \| Oil
Derivative [Line Items]
Derivative, nonmonetary notional amount, energy measure \| Boe	1,752	778
Chicago Mercantile Exchange (CME) \| Derivative instruments not designated as hedging instruments \| Commodity contracts \| Natural Gas
Derivative [Line Items]
Derivative, nonmonetary notional amount, energy measure \| MMBTU	6,075	6,290

Number of Companies that Issued the Warrants (Issuers Portion Only)

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The aggregate fair value of assets that are already posted, at the end of the reporting period, as collateral for derivative instruments with credit-risk-related contingent features.

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Average remaining period until maturity of the derivative contract, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Nominal energy measure used to calculate payments on a derivative instrument.

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