Shareholders Equity and Dividend Restrictions (Details) - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statutory Accounting Practices [Line Items]
Statutory net income	$ 3.8	$ 3.4	$ 2.5
Statutory surplus	13.8	$ 12.2	$ 10.4
Minimum statutory surplus required by regulators	4.8
Investments on deposit with regulatory bodies	0.5
Maximum dividend distributions permitted in 2020 without regulatory approval	2.9
Maximum loans to parent company permitted without regulatory approval	1.0
Restricted GAAP net assets of Cigna Corporation's subsidiaries	$ 15.3