Condensed Consolidating Financial Information - Cash Flow Statements (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities	$ 6,692	$ 3,644
Cash Flows from Investing Activities
Net change in loans due to (from) affiliates	0	0
Proceeds from investments sold:
Debt and equity securities	2,639	1,930
Investment maturities and repayments:
Debt and equity securities	1,281	1,394
Commercial mortgage loans	174	181
Other sales, maturities and repayments (primarily short-term and other long-term investments)	978	588
Investments purchased or originated:
Debt and equity securities	(3,347)	(4,461)
Commercial mortgage loans	(221)	(288)
Other (primarily short-term and other long-term investments)	(1,214)	(660)
Property and equipment purchases, net	(740)	(346)
Acquisitions, net of cash acquired	(6)	0
Other, net	(7)	(12)
Net cash provided by (used in) investing activities	(463)	(1,674)
Cash Flows from Financing Activities
Net change in amounts due to (from) affiliates	0	0
Intercompany dividends paid	0	0
Deposits and interest credited to contractholder deposit funds	731	816
Withdrawals and benefit payments from contractholder deposit funds	(845)	(872)
Net change in short-term debt	(479)	(109)
Repayment of long-term debt	(3,340)	(131)
Net proceeds on issuance of long-term debt	0	19,884
Repurchase of common stock	(1,540)	(310)
Issuance of common stock	101	41
Other, net	(108)	(204)
Net cash provided by (used in) financing activities	(5,480)	19,115
Effect of foreign currency rate changes on cash and cash equivalents	(27)	(25)
Net increase in cash and cash equivalents	722	21,060
Cash and cash equivalents, January 1,	3,855	2,972
Cash and cash equivalents, ending balance	4,577	24,032
Consolidation, Eliminations [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities	(3,955)	(1,374)
Cash Flows from Investing Activities
Net change in loans due to (from) affiliates	466	(153)
Proceeds from investments sold:
Debt and equity securities	0	0
Investment maturities and repayments:
Debt and equity securities	0	0
Commercial mortgage loans	0	0
Other sales, maturities and repayments (primarily short-term and other long-term investments)	0	0
Investments purchased or originated:
Debt and equity securities	0	0
Commercial mortgage loans	0	0
Other (primarily short-term and other long-term investments)	0	0
Property and equipment purchases, net	0	0
Acquisitions, net of cash acquired	0
Other, net	0	0
Net cash provided by (used in) investing activities	466	(153)
Cash Flows from Financing Activities
Net change in amounts due to (from) affiliates	(466)	153
Intercompany dividends paid	3,955	1,374
Deposits and interest credited to contractholder deposit funds	0	0
Withdrawals and benefit payments from contractholder deposit funds	0	0
Net change in short-term debt	0	0
Repayment of long-term debt	0	0
Net proceeds on issuance of long-term debt		0
Repurchase of common stock	0	0
Issuance of common stock	0	0
Other, net	0	0
Net cash provided by (used in) financing activities	3,489	1,527
Effect of foreign currency rate changes on cash and cash equivalents	0	0
Net increase in cash and cash equivalents	0	0
Cash and cash equivalents, January 1,	0	0
Cash and cash equivalents, ending balance	0	0
Cigna [Member] | Reportable Legal Entities [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities	1,256	5
Cash Flows from Investing Activities
Net change in loans due to (from) affiliates	0	0
Proceeds from investments sold:
Debt and equity securities	0	0
Investment maturities and repayments:
Debt and equity securities	0	0
Commercial mortgage loans	0	0
Other sales, maturities and repayments (primarily short-term and other long-term investments)	0	0
Investments purchased or originated:
Debt and equity securities	0	0
Commercial mortgage loans	0	0
Other (primarily short-term and other long-term investments)	(5)	0
Property and equipment purchases, net	0	0
Acquisitions, net of cash acquired	0
Other, net	0	0
Net cash provided by (used in) investing activities	(5)	0
Cash Flows from Financing Activities
Net change in amounts due to (from) affiliates	903	0
Intercompany dividends paid	0	0
Deposits and interest credited to contractholder deposit funds	0	0
Withdrawals and benefit payments from contractholder deposit funds	0	0
Net change in short-term debt	1,140	0
Repayment of long-term debt	(2,003)	0
Net proceeds on issuance of long-term debt		19,884
Repurchase of common stock	(1,540)	0
Issuance of common stock	101	0
Other, net	(95)	0
Net cash provided by (used in) financing activities	(1,494)	19,884
Effect of foreign currency rate changes on cash and cash equivalents	0	0
Net increase in cash and cash equivalents	(243)	19,889
Cash and cash equivalents, January 1,	243	0
Cash and cash equivalents, ending balance	0	19,889
Old Cigna [Member] | Reportable Legal Entities [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities	2,259	1,113
Cash Flows from Investing Activities
Net change in loans due to (from) affiliates	1,695	(275)
Proceeds from investments sold:
Debt and equity securities	0	0
Investment maturities and repayments:
Debt and equity securities	0	0
Commercial mortgage loans	0	0
Other sales, maturities and repayments (primarily short-term and other long-term investments)	0	53
Investments purchased or originated:
Debt and equity securities	0	0
Commercial mortgage loans	0	0
Other (primarily short-term and other long-term investments)	0	0
Property and equipment purchases, net	0	0
Acquisitions, net of cash acquired	0
Other, net	0	0
Net cash provided by (used in) investing activities	1,695	(222)
Cash Flows from Financing Activities
Net change in amounts due to (from) affiliates	(537)	(428)
Intercompany dividends paid	(1,917)	0
Deposits and interest credited to contractholder deposit funds	0	0
Withdrawals and benefit payments from contractholder deposit funds	0	0
Net change in short-term debt	(1,500)	(5)
Repayment of long-term debt	0	(131)
Net proceeds on issuance of long-term debt		0
Repurchase of common stock	0	(310)
Issuance of common stock	0	41
Other, net	0	(67)
Net cash provided by (used in) financing activities	(3,954)	(900)
Effect of foreign currency rate changes on cash and cash equivalents	0	0
Net increase in cash and cash equivalents	0	(9)
Cash and cash equivalents, January 1,	0	9
Cash and cash equivalents, ending balance	0	0
Express Scripts Holding Company [Member] | Reportable Legal Entities [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities	72	0
Cash Flows from Investing Activities
Net change in loans due to (from) affiliates	(2,698)	0
Proceeds from investments sold:
Debt and equity securities	0	0
Investment maturities and repayments:
Debt and equity securities	0	0
Commercial mortgage loans	0	0
Other sales, maturities and repayments (primarily short-term and other long-term investments)	0	0
Investments purchased or originated:
Debt and equity securities	0	0
Commercial mortgage loans	0	0
Other (primarily short-term and other long-term investments)	(402)	0
Property and equipment purchases, net	0	0
Acquisitions, net of cash acquired	0
Other, net	0	0
Net cash provided by (used in) investing activities	(3,100)	0
Cash Flows from Financing Activities
Net change in amounts due to (from) affiliates	3,825	0
Intercompany dividends paid	0	0
Deposits and interest credited to contractholder deposit funds	0	0
Withdrawals and benefit payments from contractholder deposit funds	0	0
Net change in short-term debt	0	0
Repayment of long-term debt	(1,000)	0
Net proceeds on issuance of long-term debt		0
Repurchase of common stock	0	0
Issuance of common stock	0	0
Other, net	0	0
Net cash provided by (used in) financing activities	2,825	0
Effect of foreign currency rate changes on cash and cash equivalents	0	0
Net increase in cash and cash equivalents	(203)	0
Cash and cash equivalents, January 1,	633	0
Cash and cash equivalents, ending balance	430	0
Express Scripts Incorporated [Member] | Reportable Legal Entities [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities	4,087	0
Cash Flows from Investing Activities
Net change in loans due to (from) affiliates	0	0
Proceeds from investments sold:
Debt and equity securities	0	0
Investment maturities and repayments:
Debt and equity securities	0	0
Commercial mortgage loans	0	0
Other sales, maturities and repayments (primarily short-term and other long-term investments)	0	0
Investments purchased or originated:
Debt and equity securities	0	0
Commercial mortgage loans	0	0
Other (primarily short-term and other long-term investments)	0	0
Property and equipment purchases, net	(232)	0
Acquisitions, net of cash acquired	0
Other, net	0	0
Net cash provided by (used in) investing activities	(232)	0
Cash Flows from Financing Activities
Net change in amounts due to (from) affiliates	(3,537)	0
Intercompany dividends paid	0	0
Deposits and interest credited to contractholder deposit funds	0	0
Withdrawals and benefit payments from contractholder deposit funds	0	0
Net change in short-term debt	(8)	0
Repayment of long-term debt	(337)	0
Net proceeds on issuance of long-term debt		0
Repurchase of common stock	0	0
Issuance of common stock	0	0
Other, net	0	0
Net cash provided by (used in) financing activities	(3,882)	0
Effect of foreign currency rate changes on cash and cash equivalents	0	0
Net increase in cash and cash equivalents	(27)	0
Cash and cash equivalents, January 1,	43	0
Cash and cash equivalents, ending balance	16	0
Medco Health Solutions Incorporated [Member] | Reportable Legal Entities [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities	43	0
Cash Flows from Investing Activities
Net change in loans due to (from) affiliates	0	0
Proceeds from investments sold:
Debt and equity securities	0	0
Investment maturities and repayments:
Debt and equity securities	0	0
Commercial mortgage loans	0	0
Other sales, maturities and repayments (primarily short-term and other long-term investments)	0	0
Investments purchased or originated:
Debt and equity securities	0	0
Commercial mortgage loans	0	0
Other (primarily short-term and other long-term investments)	0	0
Property and equipment purchases, net	0	0
Acquisitions, net of cash acquired	0
Other, net	0	0
Net cash provided by (used in) investing activities	0	0
Cash Flows from Financing Activities
Net change in amounts due to (from) affiliates	(43)	0
Intercompany dividends paid	0	0
Deposits and interest credited to contractholder deposit funds	0	0
Withdrawals and benefit payments from contractholder deposit funds	0	0
Net change in short-term debt	0	0
Repayment of long-term debt	0	0
Net proceeds on issuance of long-term debt		0
Repurchase of common stock	0	0
Issuance of common stock	0	0
Other, net	0	0
Net cash provided by (used in) financing activities	(43)	0
Effect of foreign currency rate changes on cash and cash equivalents	0	0
Net increase in cash and cash equivalents	0	0
Cash and cash equivalents, January 1,	0	0
Cash and cash equivalents, ending balance	0	0
Non-Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities	2,930	3,900
Cash Flows from Investing Activities
Net change in loans due to (from) affiliates	537	428
Proceeds from investments sold:
Debt and equity securities	2,639	1,930
Investment maturities and repayments:
Debt and equity securities	1,281	1,394
Commercial mortgage loans	174	181
Other sales, maturities and repayments (primarily short-term and other long-term investments)	978	535
Investments purchased or originated:
Debt and equity securities	(3,347)	(4,461)
Commercial mortgage loans	(221)	(288)
Other (primarily short-term and other long-term investments)	(807)	(660)
Property and equipment purchases, net	(508)	(346)
Acquisitions, net of cash acquired	(6)
Other, net	(7)	(12)
Net cash provided by (used in) investing activities	713	(1,299)
Cash Flows from Financing Activities
Net change in amounts due to (from) affiliates	(145)	275
Intercompany dividends paid	(2,038)	(1,374)
Deposits and interest credited to contractholder deposit funds	731	816
Withdrawals and benefit payments from contractholder deposit funds	(845)	(872)
Net change in short-term debt	(111)	(104)
Repayment of long-term debt	0	0
Net proceeds on issuance of long-term debt		0
Repurchase of common stock	0	0
Issuance of common stock	0	0
Other, net	(13)	(137)
Net cash provided by (used in) financing activities	(2,421)	(1,396)
Effect of foreign currency rate changes on cash and cash equivalents	(27)	(25)
Net increase in cash and cash equivalents	1,195	1,180
Cash and cash equivalents, January 1,	2,936	2,963
Cash and cash equivalents, ending balance	$ 4,131	$ 4,143