Fair Value of Assets and Liabilities Fair Value of Assets and Liabilities (Fair Value Assets Measured on Non-Recurring Basis) (Details) - Partnership Interest [Member] - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Assets Carrying Value Prior To Impairment	[1]	$ 17,785	$ 2,246	$ 17,785	$ 2,246
Fair Value Assets Gains Losses	[1]	$ (3,537)	$ (1,860)	$ (8,586)	$ (1,860)

[1] The impaired limited partnership interests presented above were accounted for using the cost method. Impairments on these cost method investments were recognized at estimated fair value determined using the net asset values of the Company’s ownership interest as provided in the financial statements of the investees. The market for these investments has limited activity and price transparency.