Shareholders Equity and Dividend Restrictions (Details) - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statutory Accounting Practices [Line Items]
Statutory net income	$ 2.0	$ 2.1	$ 2.0
Statutory surplus	8.5	$ 8.0	$ 7.5
Minimum statutory surplus required by regulators	2.7
Investments on deposit with regulatory bodies	0.5
Maximum dividend distributions permitted in 2017 without state approval	1.6
Maximum loans to parent company permitted without state approval	1.3
Restricted net assets of Cigna Corporation	$ 8.8