Schedule I - Summary of Investments Other Than investments in Related Parties (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Schedule of Investments [Line Items]
Amortized Cost	$ 5,283,266	$ 5,244,903
Fair Value	5,681,970	5,199,595
Equity securities, at cost	6,360	31,824
Equity securities, at fair value	10,494	36,922
Fixed maturities, trading, amortized cost	59,995	44,759
Fixed maturities, trading	59,964	41,627
Commercial mortgage and other loans	1,239,885	1,209,150
Policy loans	1,314,064	1,236,077
Other invested assets	429,558	377,429
Total Investment at Cost	8,333,128
Total investment per Balance Sheet	8,735,935	8,100,800
Fixed Maturities
Schedule of Investments [Line Items]
Amortized Cost	5,283,266	5,244,903
Fair Value	5,681,970	5,199,595
Equity securities
Schedule of Investments [Line Items]
Equity securities, at cost	6,360
Equity securities, at fair value	10,494
Available-for-sale Securities \| Fixed Maturities
Schedule of Investments [Line Items]
Amortized Cost	5,283,266
Fair Value	5,681,970
Trading \| Fixed Maturities
Schedule of Investments [Line Items]
Fixed maturities, trading, amortized cost	59,995
Fixed maturities, trading	59,964
U.S. Treasury securities and obligations of U.S. government authorities and agencies \| Fixed Maturities
Schedule of Investments [Line Items]
Amortized Cost	83,622	75,049
Fair Value	86,468	77,470
Obligations of U.S. states and their political subdivisions \| Fixed Maturities
Schedule of Investments [Line Items]
Amortized Cost	458,152	609,955
Fair Value	497,827	622,758
Foreign government bonds \| Fixed Maturities
Schedule of Investments [Line Items]
Amortized Cost	196,034	208,009
Fair Value	222,826	201,947
Asset-backed securities \| Fixed Maturities
Schedule of Investments [Line Items]
Amortized Cost	119,602	156,818
Fair Value	119,936	157,596
Residential mortgage-backed securities \| Fixed Maturities
Schedule of Investments [Line Items]
Amortized Cost	60,778	88,862
Fair Value	63,804	89,063
Commercial mortgage-backed securities \| Fixed Maturities
Schedule of Investments [Line Items]
Amortized Cost	367,848	347,570
Fair Value	382,916	$ 346,396
Public utilities \| Available-for-sale Securities \| Fixed Maturities
Schedule of Investments [Line Items]
Amortized Cost	737,155
Fair Value	810,229
All other corporate bonds \| Available-for-sale Securities \| Fixed Maturities
Schedule of Investments [Line Items]
Amortized Cost	3,257,754
Fair Value	3,495,397
Redeemable preferred stock \| Available-for-sale Securities \| Fixed Maturities
Schedule of Investments [Line Items]
Amortized Cost	2,321
Fair Value	2,567
Other common stocks \| Equity securities
Schedule of Investments [Line Items]
Equity securities, at cost	1,008
Equity securities, at fair value	3,467
Mutual funds \| Equity securities
Schedule of Investments [Line Items]
Equity securities, at cost	376
Equity securities, at fair value	459
Perpetual preferred stocks \| Equity securities
Schedule of Investments [Line Items]
Equity securities, at cost	4,976
Equity securities, at fair value	$ 6,568

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