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Variable Interest Entities - Additional Information (Details) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Variable Interest Entity [Line Items]
Investments in operating partnerships	$ 269,000,000		$ 248,000,000
Liabilities related to investments in qualified affordable housing projects	2,000,000		2,000,000
Recurring [Member]
Variable Interest Entity [Line Items]
Other investments	103,000,000		115,000,000
LIHTC Investments [Member]
Variable Interest Entity [Line Items]
Investments in operating partnerships	5,948,000,000		5,932,000,000
Liabilities related to investments in qualified affordable housing projects	2,568,000,000		2,569,000,000
Tax credit of investment	40,000,000
LIHTC Investments [Member] \| Qualified affordable housing projects investment [Member]
Variable Interest Entity [Line Items]
Liabilities related to investments in qualified affordable housing projects	499,000,000		532,000,000
LIHTC Investments [Member] \| Accrued Income And Other Assets [Member]
Variable Interest Entity [Line Items]
Investments in operating partnerships	1,400,000,000		1,400,000,000
LIHTC Investments [Member] \| Investments [Member]
Variable Interest Entity [Line Items]
Amortization of investment	46,000,000	$ 41,000,000
Tax credit of investment	45,000,000
Guaranteed Funds [Member] \| Investments [Member]
Variable Interest Entity [Line Items]
VIE, assets that can only be used to settle obligations	0		0
VIE, liabilities	0		0
Measured at NAV [Member] \| Recurring [Member] \| Principal Investments Indirect [Member]
Variable Interest Entity [Line Items]
Other investments	$ 83,000,000		$ 96,000,000