Derivatives (Notional and Fair Values) (Details) MMBTU in Thousands, Boe in Thousands, $ in Thousands	6 Months Ended	12 Months Ended
Jun. 30, 2019 USD ($) MMBTU Boe company	Dec. 31, 2018 USD ($) MMBTU Boe company
Derivative Asset [Abstract]
Derivative assets - Fair value	$ 242,876	$ 107,816
Less: Master netting agreements	(40,372)	(31,569)
Less: Cash collateral received/paid	(3,831)	(13,577)
Derivative asset, after netting	198,673	62,670
Derivative Liability [Abstract]
Derivative liabilities - Fair value	172,923	118,305
Less: Master netting agreements	(40,372)	(31,569)
Less: Cash collateral received/paid	(34,122)	(6,833)
Derivative liability, after netting	$ 98,429	$ 79,903
Crude oil
Derivative Liability [Abstract]
Derivative, nonmonetary notional amount, energy measure \| Boe	5,646	2,507
Natural gas
Derivative Liability [Abstract]
Derivative, nonmonetary notional amount, energy measure \| MMBTU	30,775	14,722
Derivative instruments designated as hedging instruments
Derivative Instruments
Notional amount	$ 191,033	$ 126,056
Derivative Asset [Abstract]
Derivative assets - Fair value	52	0
Derivative Liability [Abstract]
Derivative liabilities - Fair value	3,019	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	3,019	5,866
Derivative instruments designated as hedging instruments \| Foreign exchange contracts
Derivative Instruments
Notional amount	160,007	90,245
Derivative Asset [Abstract]
Derivative assets - Fair value	52	0
Derivative Liability [Abstract]
Derivative liabilities - Fair value	0	611
Derivatives not designated as hedging instruments
Derivative Instruments
Notional amount	16,986,784	15,222,341
Derivative Asset [Abstract]
Derivative assets - Fair value	242,824	107,816
Derivative Liability [Abstract]
Derivative liabilities - Fair value	169,904	111,828
Derivatives not designated as hedging instruments \| Interest rate contracts
Derivative Instruments
Notional amount	13,469,821	11,695,499
Derivative Asset [Abstract]
Derivative assets - Fair value	190,388	69,818
Derivative Liability [Abstract]
Derivative liabilities - Fair value	121,352	69,267
Derivatives not designated as hedging instruments \| Foreign exchange contracts
Derivative Instruments
Notional amount	3,425,107	3,407,522
Derivative Asset [Abstract]
Derivative assets - Fair value	27,797	21,624
Derivative Liability [Abstract]
Derivative liabilities - Fair value	22,528	19,329
Derivatives not designated as hedging instruments \| Credit contracts
Derivative Instruments
Notional amount	91,856	119,320
Derivative Asset [Abstract]
Derivative assets - Fair value	3	1
Derivative Liability [Abstract]
Derivative liabilities - Fair value	118	164
Derivatives not designated as hedging instruments \| Equity contracts
Derivative Instruments
Notional amount	0	0
Derivative Asset [Abstract]
Derivative assets - Fair value	1,985	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	22,651	14,422
Derivative Liability [Abstract]
Derivative liabilities - Fair value	$ 25,906	$ 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	3	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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