Fair Value Level 3 Financial Instruments changes in Fair Value recurring basis (Details) - Fair Value, Measurements, Recurring - Significant unobservable inputs (Level 3) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2019		Dec. 31, 2018
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Asset Balance at beginning of period		$ 100,414		$ 189,312
Asset Purchases		60,628		92,681
Asset Sales		(4,697)		(13,568)
Asset, Gain (Loss) Included in Earnings		0		(545)
Gain/Loss in Other Comprehensive Income (Loss)		217		(4,585)
Asset Transfers Into Level 3	[1]	3,643		7,082
Asset, Transfers out of Level 3	[1]	(124,127)		(170,182)
Asset, Amortization		(28)		219
Asset Balance at end of period		36,050		100,414
Corporate
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Asset Balance at beginning of period		22,011		33,600
Asset Purchases		6,000		0
Asset Sales		(3,344)		(9,432)
Asset, Gain (Loss) Included in Earnings		0		0
Gain/Loss in Other Comprehensive Income (Loss)		443		974
Asset Transfers Into Level 3	[1]	3,643		7,082
Asset, Transfers out of Level 3	[1]	(22,137)		(8,530)
Asset, Amortization		(28)		265
Asset Balance at end of period		6,588		22,011
Residential mortgage-backed
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Asset Balance at beginning of period		0		9,124
Asset Purchases		18,378		27,818
Asset Sales		0		0
Asset, Gain (Loss) Included in Earnings		0		0
Gain/Loss in Other Comprehensive Income (Loss)		0		0
Asset Transfers Into Level 3		0	[1]	0
Asset, Transfers out of Level 3	[1]	(18,378)		(36,942)
Asset, Amortization		0		0
Asset Balance at end of period		0		0
Commercial mortgage-backed
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Asset Balance at beginning of period		67,940		85,701
Asset Purchases		7,540		36,008
Asset Sales		(376)		(1,337)
Asset, Gain (Loss) Included in Earnings		0		0
Gain/Loss in Other Comprehensive Income (Loss)		578		3,599
Asset Transfers Into Level 3		0		0
Asset, Transfers out of Level 3	[1]	(62,902)		(48,787)
Asset, Amortization		0		(46)
Asset Balance at end of period		12,780		67,940
Other asset-backed
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Asset Balance at beginning of period		3,601		53,480
Asset Purchases		28,710		28,855
Asset Sales		(977)		(2,799)
Asset, Gain (Loss) Included in Earnings		0		0
Gain/Loss in Other Comprehensive Income (Loss)		(869)		12
Asset Transfers Into Level 3		0		0
Asset, Transfers out of Level 3	[1]	(20,710)		(75,923)
Asset, Amortization		0		0
Asset Balance at end of period		9,755		3,601
Non-redeemable preferred stocks
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Asset Balance at beginning of period		6,862		7,407
Asset Purchases		0		0
Asset Sales		0		0
Asset, Gain (Loss) Included in Earnings		0		(545)
Gain/Loss in Other Comprehensive Income (Loss)		65		0
Asset Transfers Into Level 3		0		0
Asset, Transfers out of Level 3		0		0
Asset, Amortization		0		0
Asset Balance at end of period		6,927		6,862
Index Product Embedded Derivatives
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Liability Value beginning of period		40,028		27,774
Liability, Purchases		15,325		11,514
Liability, Settlements		(7,014)		(4,447)
Liability, Gain (Loss) Included in Earnings		28,007		(5,187)
Liability, Gain (Loss) Included in Other Comprehensive Income (Loss)		0		0
Liability, Transfers Into Level 3	[1]	0		0
Liability, Transfers out of Level 3	[1]	0		0
Liability Value end of period		$ 76,346		$ 40,028

[1] Transfers into Level 3 represent assets previously priced using an external pricing service with access to observable inputs no longer available and therefore, were priced using non-binding broker quotes. Transfers out of Level 3 include those assets that we are now able to obtain pricing from a third-party pricing vendor that uses observable inputs. The fair values of newly issued securities often require additional estimation until a market is created, which is generally within a few months after issuance. Once a market is created, as was the case for the majority of the security transfers out of the Level 3 category above, Level 2 valuation sources become available.