Derivatives (Notional and Fair Values) (Details) MMBTU in Thousands, Boe in Thousands, $ in Thousands	Mar. 31, 2019 USD ($) MMBTU Boe company	Dec. 31, 2018 USD ($) MMBTU Boe company
Derivative Asset [Abstract]
Derivative assets - Fair value	$ 135,782	$ 107,816
Less: Master netting agreements	(39,118)	(31,569)
Less: Cash collateral received/paid	(920)	(13,577)
Derivative asset, after netting	95,744	62,670
Derivative Liability [Abstract]
Derivative liabilities - Fair value	109,587	118,305
Less: Master netting agreements	(39,118)	(31,569)
Less: Cash collateral received/paid	(16,984)	(6,833)
Derivative liability, after netting	$ 53,485	$ 79,903
Oil
Derivative Liability [Abstract]
Derivative, nonmonetary notional amount \| Boe	4,178	2,507
Natural gas
Derivative Liability [Abstract]
Derivative, nonmonetary notional amount \| MMBTU	20,679	14,722
Derivative instruments designated as hedging instruments
Derivative Instruments
Notional amount	$ 123,241	$ 126,056
Derivative Asset [Abstract]
Derivative assets - Fair value	0	0
Derivative Liability [Abstract]
Derivative liabilities - Fair value	4,678	6,477
Derivative instruments designated as hedging instruments \| Interest rate contracts
Derivative Instruments
Notional amount	31,026	35,811
Derivative Asset [Abstract]
Derivative assets - Fair value	0	0
Derivative Liability [Abstract]
Derivative liabilities - Fair value	4,660	5,866
Derivative instruments designated as hedging instruments \| Foreign exchange contracts
Derivative Instruments
Notional amount	92,215	90,245
Derivative Asset [Abstract]
Derivative assets - Fair value	0	0
Derivative Liability [Abstract]
Derivative liabilities - Fair value	18	611
Derivatives not designated as hedging instruments
Derivative Instruments
Notional amount	15,873,400	15,222,341
Derivative Asset [Abstract]
Derivative assets - Fair value	135,782	107,816
Derivative Liability [Abstract]
Derivative liabilities - Fair value	104,909	111,828
Derivatives not designated as hedging instruments \| Interest rate contracts
Derivative Instruments
Notional amount	12,266,761	11,695,499
Derivative Asset [Abstract]
Derivative assets - Fair value	96,256	69,818
Derivative Liability [Abstract]
Derivative liabilities - Fair value	71,912	69,267
Derivatives not designated as hedging instruments \| Foreign exchange contracts
Derivative Instruments
Notional amount	3,513,714	3,407,522
Derivative Asset [Abstract]
Derivative assets - Fair value	30,085	21,624
Derivative Liability [Abstract]
Derivative liabilities - Fair value	24,900	19,329
Derivatives not designated as hedging instruments \| Credit contracts
Derivative Instruments
Notional amount	92,925	119,320
Derivative Asset [Abstract]
Derivative assets - Fair value	1	1
Derivative Liability [Abstract]
Derivative liabilities - Fair value	81	164
Derivatives not designated as hedging instruments \| Equity contracts
Derivative Instruments
Notional amount	0	0
Derivative Asset [Abstract]
Derivative assets - Fair value	2,201	1,951
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	7,239	14,422
Derivative Liability [Abstract]
Derivative liabilities - Fair value	$ 8,016	$ 23,068
Derivatives not designated as hedging instruments \| Equity, Public Companies
Derivative Liability [Abstract]
Number of companies that issued the equity (issuers portion only) \| company	4	4
Derivatives not designated as hedging instruments \| Equity, Private Companies
Derivative Liability [Abstract]
Number of companies that issued the equity (issuers portion only) \| company	17	18

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

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Aggregate notional amount of derivative expressed in nonmonetary units. For example, the number of barrels specified in a fuel oil forward purchase contract.

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Fair value of liability associated with financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset.

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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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