v3.8.0.1
Investments - Contractual Maturities (Details) - USD ($)
$ in Thousands
Sep. 30, 2017
Dec. 31, 2016
HTM fixed maturities, Amortized cost    
Due in one year or less $ 49,293  
Due after one year through five years 335,922  
Due after five years through ten years 723,297  
Due after ten years 9,856  
Total before securities without single maturities, Amortized cost 1,118,368  
Fixed Maturities, held-to-maturity, Amortized cost 1,118,368  
HTM fixed maturities, Fair value    
Due in one year or less 49,298  
Due after one year through five years 346,747  
Due after five years through ten years 746,131  
Due after ten years 9,930  
Total before securities without single maturities, Fair value 1,152,106  
Fixed maturities, held-to-maturity securities, fair value 1,152,106 $ 766,135
AFS fixed maturities, Amortized cost    
Due in one year or less 40,440  
Due after one year through five years 577,760  
Due after five years through ten years 961,682  
Due after five years through ten years 2,500  
Total before securities without single maturities, Amortized cost 1,582,382  
Fixed Maturities, available-for-sale, Original or amortized cost 3,844,996 4,005,642
AFS fixed maturities, Fair value    
Due in one year or less 38,784  
Due after one year through five years 583,569  
Due after five years through ten years 990,968  
Due after ten years 2,603  
Total before securities without single maturities, Fair value 1,615,924  
Fixed Maturities, available-for-sale, Fair value 3,884,587 3,971,666
U.S. agency bonds – mortgage-backed [Member]    
HTM fixed maturities, Amortized cost    
Amortized cost of securities without single maturities 0  
HTM fixed maturities, Fair value    
Fair value of securities without single maturities 0  
AFS fixed maturities, Amortized cost    
Amortized cost of securities without single maturities 2,004,645  
Fixed Maturities, available-for-sale, Original or amortized cost 2,004,645 1,720,436
AFS fixed maturities, Fair value    
Fair value of securities without single maturities 2,006,402  
Fixed Maturities, available-for-sale, Fair value 2,006,402 1,716,038
Asset-backed securities [Member]    
HTM fixed maturities, Amortized cost    
Amortized cost of securities without single maturities 0  
HTM fixed maturities, Fair value    
Fair value of securities without single maturities 0  
AFS fixed maturities, Amortized cost    
Amortized cost of securities without single maturities 257,969  
Fixed Maturities, available-for-sale, Original or amortized cost 257,969 217,232
AFS fixed maturities, Fair value    
Fair value of securities without single maturities 262,261  
Fixed Maturities, available-for-sale, Fair value $ 262,261 $ 220,876