Condensed Consolidating Financial Information - Cash Flow Statements (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities	$ 4,231	$ 3,020
Cash Flows from Investing Activities
Net change in loans due to (from) affiliates	0	0
Proceeds from investments sold:
Debt and equity securities	2,036	1,273
Investment maturities and repayments:
Debt and equity securities	738	887
Commercial mortgage loans	169	88
Other sales, maturities and repayments (primarily short-term and other long-term investments)	650	412
Investments purchased or originated:
Debt and equity securities	(2,212)	(3,544)
Commercial mortgage loans	(184)	(194)
Other (primarily short-term and other long-term investments)	(847)	(501)
Property and equipment purchases, net	(497)	(220)
Acquisitions, net of cash acquired	(6)	0
Other, net	(6)	0
Net cash provided by (used in) investing activities	(159)	(1,799)
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	498	574
Withdrawals and benefit payments from contractholder deposit funds	(542)	(594)
Net change in short-term debt	(621)	(5)
Repayment of long-term debt	(2,740)	(131)
Repurchase of common stock	(866)	(310)
Issuance of common stock	70	27
Other, net	(106)	(103)
Net cash provided by (used in) financing activities	(4,307)	(542)
Effect of foreign currency rate changes on cash and cash equivalents	(10)	(17)
Net increase in cash and cash equivalents	(245)	662
Cash and cash equivalents, January 1,	3,855	2,972
Cash and cash equivalents, ending balance	3,610	3,634
Consolidation, Eliminations [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities	(2,769)	(896)
Cash Flows from Investing Activities
Net change in loans due to (from) affiliates	(73)	(301)
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
Net cash provided by (used in) investing activities	(73)	(301)
Cash Flows from Financing Activities
Net change in amounts due to (from) affiliates	73	301
Intercompany dividends paid	2,725	896
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
Repurchase of common stock	0	0
Issuance of common stock	0	0
Other, net	44	0
Net cash provided by (used in) financing activities	2,842	1,197
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	771	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)	(16)	0
Property and equipment purchases, net	0	0
Acquisitions, net of cash acquired	0
Other, net	0
Net cash provided by (used in) investing activities	(16)	0
Cash Flows from Financing Activities
Net change in amounts due to (from) affiliates	305	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	990	0
Repayment of long-term debt	(1,403)	0
Repurchase of common stock	(866)	0
Issuance of common stock	70	0
Other, net	(94)	0
Net cash provided by (used in) financing activities	(998)	0
Effect of foreign currency rate changes on cash and cash equivalents	0	0
Net increase in cash and cash equivalents	(243)	0
Cash and cash equivalents, January 1,	243	0
Cash and cash equivalents, ending balance	0	0
Old Cigna [Member] | Reportable Legal Entities [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities	1,732	885
Cash Flows from Investing Activities
Net change in loans due to (from) affiliates	1,600	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	43
Investments purchased or originated:
Debt and equity securities	0	0
Commercial mortgage loans	0	0
Other (primarily short-term and other long-term investments)	(6)	0
Property and equipment purchases, net	0	0
Acquisitions, net of cash acquired	0
Other, net	0
Net cash provided by (used in) investing activities	1,594	43
Cash Flows from Financing Activities
Net change in amounts due to (from) affiliates	(478)	(301)
Intercompany dividends paid	(1,348)	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)
Repurchase of common stock	0	(310)
Issuance of common stock	0	27
Other, net	0	(177)
Net cash provided by (used in) financing activities	(3,326)	(897)
Effect of foreign currency rate changes on cash and cash equivalents	0	0
Net increase in cash and cash equivalents	0	31
Cash and cash equivalents, January 1,	0	9
Cash and cash equivalents, ending balance	0	40
Express Scripts Holding Company [Member] | Reportable Legal Entities [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities	103	0
Cash Flows from Investing Activities
Net change in loans due to (from) affiliates	(2,005)	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)	(31)	0
Property and equipment purchases, net	0	0
Acquisitions, net of cash acquired	0
Other, net	0
Net cash provided by (used in) investing activities	(2,036)	0
Cash Flows from Financing Activities
Net change in amounts due to (from) affiliates	2,821	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
Repurchase of common stock	0	0
Issuance of common stock	0	0
Other, net	0	0
Net cash provided by (used in) financing activities	1,821	0
Effect of foreign currency rate changes on cash and cash equivalents	0	0
Net increase in cash and cash equivalents	(112)	0
Cash and cash equivalents, January 1,	633	0
Cash and cash equivalents, ending balance	521	0
Express Scripts Incorporated [Member] | Reportable Legal Entities [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities	3,312	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	(147)	0
Acquisitions, net of cash acquired	0
Other, net	0
Net cash provided by (used in) investing activities	(147)	0
Cash Flows from Financing Activities
Net change in amounts due to (from) affiliates	(2,825)	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	(5)	0
Repayment of long-term debt	(337)	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	(3,167)	0
Effect of foreign currency rate changes on cash and cash equivalents	0	0
Net increase in cash and cash equivalents	(2)	0
Cash and cash equivalents, January 1,	43	0
Cash and cash equivalents, ending balance	41	0
Medco Health Solutions Incorporated [Member] | Reportable Legal Entities [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities	(528)	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
Net cash provided by (used in) investing activities	0	0
Cash Flows from Financing Activities
Net change in amounts due to (from) affiliates	528	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
Repurchase of common stock	0	0
Issuance of common stock	0	0
Other, net	0	0
Net cash provided by (used in) financing activities	528	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	1,610	3,031
Cash Flows from Investing Activities
Net change in loans due to (from) affiliates	478	301
Proceeds from investments sold:
Debt and equity securities	2,036	1,273
Investment maturities and repayments:
Debt and equity securities	738	887
Commercial mortgage loans	169	88
Other sales, maturities and repayments (primarily short-term and other long-term investments)	650	369
Investments purchased or originated:
Debt and equity securities	(2,212)	(3,544)
Commercial mortgage loans	(184)	(194)
Other (primarily short-term and other long-term investments)	(794)	(501)
Property and equipment purchases, net	(350)	(220)
Acquisitions, net of cash acquired	(6)
Other, net	(6)
Net cash provided by (used in) investing activities	519	(1,541)
Cash Flows from Financing Activities
Net change in amounts due to (from) affiliates	(424)	0
Intercompany dividends paid	(1,377)	(896)
Deposits and interest credited to contractholder deposit funds	498	574
Withdrawals and benefit payments from contractholder deposit funds	(542)	(594)
Net change in short-term debt	(106)	0
Repayment of long-term debt	0	0
Repurchase of common stock	0	0
Issuance of common stock	0	0
Other, net	(56)	74
Net cash provided by (used in) financing activities	(2,007)	(842)
Effect of foreign currency rate changes on cash and cash equivalents	(10)	(17)
Net increase in cash and cash equivalents	112	631
Cash and cash equivalents, January 1,	2,936	2,963
Cash and cash equivalents, ending balance	$ 3,048	$ 3,594