Derivative Instruments (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($) security	Dec. 31, 2017 USD ($)
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months	$ 37
Cash flow hedge, reclassified to earnings, net	$ 0	$ 0
Credit default swaps, number of instruments | security	0
Exposure Associated With Collateralization Events	$ 0	$ 0
Maximum [Member]
Non-performance Risk Adjustment	$ 1