Recent Accounting Pronouncements (Narrative) (Details) - USD ($) $ in Millions	Jun. 30, 2020	Apr. 01, 2020	Mar. 31, 2020	Jan. 01, 2020	Dec. 31, 2019	Jun. 30, 2019	Apr. 01, 2019	Mar. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effects of adoption of accounting standards	$ (84,791)				$ (83,874)	$ (77,830)
Retained Earnings [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effects of adoption of accounting standards	$ (53,420)		$ (51,516)		$ (50,695)	$ (46,425)		$ (44,379)		$ (41,983)
Cumulative Effect, Period of Adoption, Adjustment [Member] | Retained Earnings [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effects of adoption of accounting standards		$ 0					$ 0		$ 0
Cumulative Effect, Period of Adoption, Adjustment [Member] | Retained Earnings [Member] | Accounting Standards Update 2016-13 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effects of adoption of accounting standards				$ 124