Investments (Schedule Of Amortized Cost And Estimated Fair Value Of Fixed Maturity Securities By Contractual Maturity Date) (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Document Period End Date	Jun. 30, 2019
Investment Maturity Period	1 year	1 year
Due in one year or less, amortized cost	$ 457,283
Due after one year through five years, amortized cost	1,348,961
Due after five years through ten years, amortized cost	2,078,025
Due after ten years, amortized cost	3,269,532
Amortized cost, sub-total	7,153,801
Total fixed maturities, amortized cost	11,133,725	$ 11,030,800
Due in one year or less, estimated fair value	454,221
Due after one year through five years, estimated fair value	1,380,636
Due after five years through ten years, estimated fair value	2,188,372
Due after ten years, estimated fair value	3,556,224
Estimated fair value, sub-total	7,579,453
Total fixed maturities, estimated fair value	11,642,212	11,120,884
Commercial Mortgage-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, amortized cost	1,709,453
Total fixed maturities, amortized cost	1,709,453	1,691,572
Fixed maturities, estimated fair value	1,758,022
Total fixed maturities, estimated fair value	1,758,022	1,650,199
Residential Mortgage-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, amortized cost	877,279
Total fixed maturities, amortized cost	877,279	886,501
Fixed maturities, estimated fair value	909,969
Total fixed maturities, estimated fair value	909,969	880,172
Asset-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, amortized cost	11,150
Total fixed maturities, amortized cost	11,150	19,614
Fixed maturities, estimated fair value	11,196
Total fixed maturities, estimated fair value	11,196	19,408
Fixed Maturities [Member]
Debt Securities, Available-for-sale [Line Items]
Total fixed maturities, amortized cost	9,751,683	9,950,773
Total fixed maturities, estimated fair value	$ 10,258,640	$ 10,043,188