Business Combinations and Assumption of Insured Portfolio - Schedule of Recognized Identifiable Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Millions	Oct. 01, 2019	Dec. 31, 2019	Dec. 31, 2018
Liabilities assumed:
Goodwill recognized from BlueMountain acquisition		$ 117	$ 0
BlueMountain Capital Management, LLC [Member]
Identifiable assets acquired:
Cash purchase price	$ 157
Investments	3
Cash	12
Intangible assets	79
Other assets	59
Total assets	153
Liabilities assumed:
Compensation payables	61
Other liabilities	52
Total liabilities	113
Net assets of acquisition	40
Goodwill recognized from BlueMountain acquisition	117
Reduction in right-of-use assets for unfavorable lease terms	$ 5