Employee Incentive Plans - Restricted Stock (Details) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($) Employees $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares	Dec. 31, 2014 USD ($) $ / shares shares
Employee Incentive Plan Aggregate Disclosures [Line Items]
Compensation cost | $	$ 128	$ 111	$ 101
Restricted Stock Grants And Units [Member]
Employee Incentive Plan Aggregate Disclosures [Line Items]
Compensation cost | $	$ 40	$ 33	$ 31
Share Based Compensation Arrangement By Share Based Payment Award, Equity Instruments Other Than Options, Nonvested, Roll Forward
Outstanding - January 1 | shares	1,642	2,121	2,844
Awarded | shares	315	352	454
Vested | shares	(591)	(736)	(1,065)
Forfeited | shares	(57)	(95)	(112)
Outstanding - December 31 | shares	1,309	1,642	2,121
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Weighted Average Grant Date Fair Value Roll Forward [Abstract]
Outstanding - January 1 | $ / shares	$ 72.58	$ 53.59	$ 41.56
Awarded | $ / shares	138.61	121.93	78.99
Vested | $ / shares	50.01	41.99	32.34
Forfeited | $ / shares	92.51	68.31	52.95
Outstanding - December 31 | $ / shares	$ 97.78	$ 72.58	$ 53.59
Fair value of shares of Cigna common stock distributed upon SPS vesting | $	$ 82	$ 92	$ 85
Number of employees holding share-based payment awards | Employees	4,400
Unrecognized compensation expense related to non-vested share-based awards | $	$ 55
Period in which compensation expense will be recognized	2 years