Schedule I Summary Of Investments (Details) - USD ($) $ in Thousands		Dec. 31, 2019	Dec. 31, 2018
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Amortized Cost		$ 5,558,855
Fair Value	[1]	5,725,189
Amount Reflected on the Consolidated Balance Sheet	[1]	5,725,189
Reinvested Cash Collateral Held Under Securities Lending Agreements		25,561	$ 11,699
Loaned securities		66,442	$ 27,860
US government and agency securities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Amortized Cost		198,613
Fair Value		199,928
Amount Reflected on the Consolidated Balance Sheet		199,928
State and municipal obligations
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Amortized Cost		112,003
Fair Value		119,994
Amount Reflected on the Consolidated Balance Sheet		119,994
Corporate bonds and notes
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Amortized Cost		2,136,819
Fair Value		2,241,280
Amount Reflected on the Consolidated Balance Sheet		2,241,280
RMBS
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Amortized Cost		766,429
Fair Value		779,354
Amount Reflected on the Consolidated Balance Sheet		779,354
CMBS
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Amortized Cost		593,647
Fair Value		608,015
Amount Reflected on the Consolidated Balance Sheet		608,015
Other ABS
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Amortized Cost		760,785
Fair Value		759,129
Amount Reflected on the Consolidated Balance Sheet		759,129
Foreign government and agency securities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Amortized Cost		5,091
Fair Value		5,224
Amount Reflected on the Consolidated Balance Sheet		5,224
Total fixed-maturities available for sale
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Amortized Cost		4,573,387
Fair Value		4,712,924
Amount Reflected on the Consolidated Balance Sheet		4,712,924
Total fixed-maturities available for sale | Securities Financing Transaction, Fair Value
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Loaned securities		24,000
Trading securities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Amortized Cost		297,505
Fair Value		317,150
Amount Reflected on the Consolidated Balance Sheet		317,150
Reinvested Cash Collateral Held Under Securities Lending Agreements		25,600
Common stocks
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Amortized Cost		153,023
Fair Value		157,685
Amount Reflected on the Consolidated Balance Sheet		157,685
Total equity securities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Amortized Cost		153,023
Fair Value		157,685
Amount Reflected on the Consolidated Balance Sheet		157,685
Short-term investments
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Amortized Cost	[2]	533,184
Fair Value	[2]	533,358
Amount Reflected on the Consolidated Balance Sheet	[2]	533,358
Short-term investments | Securities Financing Transaction, Fair Value
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Loaned securities		14,900
Other invested assets
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Amortized Cost		1,756
Fair Value		4,072
Amount Reflected on the Consolidated Balance Sheet		4,072
Equity securities | Securities Financing Transaction, Fair Value
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Loaned securities		$ 27,500

[1] Includes $24.0 million of fixed maturity securities available for sale, $27.5 million of equity securities and $14.9 million of short-term securities loaned under securities lending agreements that are classified as other assets in our consolidated balance sheets.

[2] Includes cash collateral held under securities lending agreements of $25.6 million that is reinvested in money market instruments.