Investments (Held To Maturity Securities Allowance for Credit Losses by Credit Rating) (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Mar. 31, 2020	Jan. 01, 2020	Dec. 31, 2019
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Amortized Cost	$ 6,903,782			$ 7,106,245
Allowance for Credit Losses	(4,940)	$ (6,039)	$ (3,300)	0
Totals	6,898,842			$ 7,106,245
AAA
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Amortized Cost	93,438
Allowance for Credit Losses	0
Totals	93,438
AA
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Amortized Cost	1,739,557
Allowance for Credit Losses	(56)
Totals	1,739,501
A
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Amortized Cost	2,234,460
Allowance for Credit Losses	(985)
Totals	2,233,475
BBB
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Amortized Cost	2,733,811
Allowance for Credit Losses	(3,580)
Totals	2,730,231
BB and other below investment
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Amortized Cost	102,516
Allowance for Credit Losses	(319)
Totals	$ 102,197