Schedule II - Condensed Financial Information, Intercompany Liabilities (Details) - Parent Company [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Condensed Financial Statements, Captions [Line Items]
Intercompany liabilities, consisting primarily of payables to Cigna Holdings, Inc.	$ 2,980	$ 998
Cigna Holdings Incorporated [Member]
Condensed Financial Statements, Captions [Line Items]
Intercompany liabilities, consisting primarily of payables to Cigna Holdings, Inc.	$ 2,800	$ 700
Average monthly interest rate on intercompany payables	1.47%	0.93%