Variable Interest Entities ("VIE's") (Narrative) (Details)	9 Months Ended
	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Dec. 31, 2016 USD ($) contract
Variable Interest Entity [Line Items]
Carrying Amounts of our Investments in LPs and LLCs, As Recognized In Other Investments on our Consolidated Balance Sheets	$ 2,210,000,000		$ 2,230,000,000
Income Tax Credits And Other Tax Benefits From Qualified Affordable Housing Projects	2,000,000	$ 3,000,000
Number of Instruments, Liabilities | contract			1
Notional Amounts, Liabilities			$ 0
Carrying Value, Assets			200,000,000
Carrying Value, Liabilities	0		0
Limited Partnerships and Limited Liability Companies [Member]
Variable Interest Entity [Line Items]
Carrying Amounts of our Investments in LPs and LLCs, As Recognized In Other Investments on our Consolidated Balance Sheets	1,400,000,000		1,300,000,000
Carrying Amount Of Investments In Qualified Affordable Housing Projects	$ 32,000,000		$ 37,000,000