Related Party Transactions - Agent Loan Sale and Securitization (Details) - Collateralized Loan Obligations $ in Millions	Dec. 22, 2016 USD ($)
Related Party Transactions
Agent loans, fair value	$ 419
Affiliate
Related Party Transactions
Agent loans, fair value	419
Class A Notes Due March 10, 2034 | Affiliate
Related Party Transactions
Agent loans, fair value	140
Allstate New Jersey Insurance Company | Class A Notes Due March 10, 2034 | Affiliate
Related Party Transactions
Agent loans, fair value	77
American Heritage Life Insurance Company | Class A Notes Due March 10, 2034 | Affiliate
Related Party Transactions
Agent loans, fair value	37
Allstate Assurance Company | Class A Notes Due March 10, 2034 | Affiliate
Related Party Transactions
Agent loans, fair value	19
First Colonial Insurance Company | Class A Notes Due March 10, 2034 | Affiliate
Related Party Transactions
Agent loans, fair value	7
Allstate Life Insurance Company | Class B Deferrable Notes Due March 10, 2034 | Affiliate
Related Party Transactions
Agent loans, fair value	140
Allstate Life Insurance Company | Class C Deferrable Notes Due March 10, 2034 | Affiliate
Related Party Transactions
Agent loans, fair value	110
Allstate Life Insurance Company | Subordinated Notes Due March 10, 2034 | Affiliate
Related Party Transactions
Agent loans, fair value	$ 29