INVESTMENTS - Mortgage-backed Securities (Details) - Default rate	Dec. 31, 2018
30-59 day delinquent loans
Key assumptions for mortgage-backed securities
Mortgage-backed securities	0.25
60-90 day deliquent loans
Key assumptions for mortgage-backed securities
Mortgage-backed securities	0.70
91+ day deliquent loans
Key assumptions for mortgage-backed securities
Mortgage-backed securities	1.00
Current loans
Key assumptions for mortgage-backed securities
Mortgage-backed securities	0.10