Investments in Fixed Maturity Securities (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Schedule of Available-for-sale and Held-to-maturity Securities [Table] [Line Items]
Debt Securities, Held-to-maturity, Restricted	$ 1,219,000,000
Insurance-related Assessments
Schedule of Available-for-sale and Held-to-maturity Securities [Table] [Line Items]
Debt Securities, Held-to-maturity, Restricted	380,000,000
Reinsurance & Monoline Excess
Schedule of Available-for-sale and Held-to-maturity Securities [Table] [Line Items]
Debt Securities, Held-to-maturity, Restricted	36,000,000
Letters of Credit Outstanding, Amount	4,000,000
523991 Trust, Fiduciary, and Custody Activities
Schedule of Available-for-sale and Held-to-maturity Securities [Table] [Line Items]
Debt Securities, Held-to-maturity, Restricted	1,639,000,000
Residential mortgage-backed
Schedule of Available-for-sale and Held-to-maturity Securities [Table] [Line Items]
Gross unrealized (losses) gains for debt securities	$ 314,347	$ (55,090)