Derivative Financial Instruments - Gross and Net Amounts Derivatives (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Asset derivatives
Gross amount	$ 86	$ 115
Counter- party netting	(1)	0
Total asset derivatives	85	115
Liability derivatives
Gross amount	(286)	(346)
Counter- party netting	3	3
Total liability derivatives	(283)	(343)
OTC derivatives
Asset derivatives
Gross amount	4	4
Counter- party netting	(4)	(3)
Cash collateral (received) pledged	1	0
Total asset derivatives	1	1
Securities collateral (received) pledged	0	0
Net amount	1	1
Liability derivatives
Gross amount	(2)	(10)
Counter- party netting	4	3
Cash collateral (received) pledged	(7)	(2)
Total liability derivatives	(5)	(9)
Securities collateral (received) pledged	0	3
Net amount	$ (5)	$ (6)

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