Fair Value Measurements (excluding Consolidated Investment Entities) - Significant Unobservable Inputs (Details) - Held for sale - Market Approach Valuation Technique - Investment contract - IUL	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Minimum
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Nonperformance risk	0.22%	0.38%
Lapses	2.00%	2.00%
Maximum
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Nonperformance risk	0.42%	0.84%
Lapses	10.00%	10.00%