Derivative Financial Instruments - Gross and Net Amounts Derivatives (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Asset derivatives
Gross amount	$ 79	$ 30
Counter- party netting	(3)	(2)
Total asset derivatives	76	28
Liability derivatives
Gross amount	(266)	(228)
Counter- party netting	1	1
Total liability derivatives	(265)	(227)
OTC derivatives
Asset derivatives
Gross amount	11	10
Counter- party netting	(4)	(3)
Cash collateral (received) pledged	(5)	(5)
Total asset derivatives	2	2
Securities collateral (received) pledged	0	0
Net amount	2	2
Liability derivatives
Gross amount	(3)	(2)
Counter- party netting	4	3
Cash collateral (received) pledged	(1)	(1)
Total liability derivatives	0	0
Securities collateral (received) pledged	0	0
Net amount	$ 0	$ 0

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