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SEGMENT INFORMATION - Reconciliation (Detail) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2017 | Jun. 30, 2016 | Jun. 30, 2017 | Jun. 30, 2016
Segment Reporting Information [Line Items] |  |  |  |
Premiums | $ 13,203 | $ 13,650 | $ 26,601 | $ 27,090
Services | 230 | 262 | 483 | 522
Revenues | 13,433 | 13,912 | 27,084 | 27,612
Investment income | 101 | 95 | 212 | 195
Total revenues | 13,534 | 14,007 | 27,296 | 27,807
Benefits | 10,889 | 11,509 | 22,215 | 22,906
Operating costs | 1,453 | 1,699 | 3,006 | 3,433
Merger termination fee and related costs, net | 0 | 27 | (947) | 61
Depreciation and amortization | 92 | 89 | 184 | 177
Total operating expenses | 12,434 | 13,324 | 24,458 | 26,577
Interest expense | 1,100 | 683 | 2,838 | 1,230
Interest expense | 58 | 47 | 107 | 94
Income (loss) before income taxes | 1,042 | 636 | 2,731 | 1,136
Individual Medicare Advantage |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 8,282 | 8,050 | 16,658 | 16,077
Group Medicare Advantage |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 1,277 | 1,085 | 2,595 | 2,162
Medicare stand-alone PDP |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 925 | 1,015 | 1,866 | 2,054
Total Medicare |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 10,484 | 10,150 | 21,119 | 20,293
Fully-insured |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 1,715 | 2,487 | 3,494 | 4,821
Specialty |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 323 | 321 | 645 | 639
Medicaid and other |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 681 | 692 | 1,343 | 1,337
Provider |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Services | 63 | 74 | 133 | 145
ASO and other |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Services | 147 | 181 | 312 | 363
Pharmacy |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Services | 20 | 7 | 38 | 14
Intersegment revenues |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenues |  |  | (11,763) | (12,356)
Total revenues | (5,896) | (6,206) |  |
Intersegment revenues | Retail |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenues |  |  | 0 | 0
Total revenues | 0 | 0 |  |
Intersegment revenues | Group and Specialty |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenues |  |  | 10 | 12
Total revenues | 5 | 6 |  |
Intersegment revenues | Healthcare Services |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenues |  |  | 11,753 | 12,344
Total revenues | 5,891 | 6,200 |  |
Intersegment revenues | Individual Commercial |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenues |  |  | 0 | 0
Total revenues | 0 | 0 |  |
Intersegment revenues | Services |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenues |  |  | (8,629) | (9,563)
Total revenues | (4,314) | (4,773) |  |
Intersegment revenues | Services | Retail |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenues |  |  | 0 | 0
Total revenues | 0 | 0 |  |
Intersegment revenues | Services | Group and Specialty |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenues |  |  | 10 | 12
Total revenues | 5 | 6 |  |
Intersegment revenues | Services | Healthcare Services |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenues |  |  | 8,619 | 9,551
Total revenues | 4,309 | 4,767 |  |
Intersegment revenues | Services | Individual Commercial |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenues |  |  | 0 | 0
Total revenues | 0 | 0 |  |
Intersegment revenues | Products |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenues |  |  | (3,134) | (2,793)
Total revenues | (1,582) | (1,433) |  |
Intersegment revenues | Products | Retail |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenues |  |  | 0 | 0
Total revenues | 0 | 0 |  |
Intersegment revenues | Products | Group and Specialty |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenues |  |  | 0 | 0
Total revenues | 0 | 0 |  |
Intersegment revenues | Products | Healthcare Services |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenues |  |  | 3,134 | 2,793
Total revenues | 1,582 | 1,433 |  |
Intersegment revenues | Products | Individual Commercial |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenues |  |  | 0 | 0
Total revenues | 0 | 0 |  |
Operating Segments | Retail |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 11,273 | 10,934 | 22,679 | 21,811
Services | 2 | 2 | 4 | 3
Revenues | 11,275 | 10,936 | 22,683 | 21,814
Investment income | 24 | 22 | 49 | 46
Total revenues | 11,299 | 10,958 | 22,732 | 21,860
Benefits | 9,672 | 9,327 | 19,723 | 18,960
Operating costs | 963 | 1,069 | 1,917 | 2,151
Merger termination fee and related costs, net |  | 0 | 0 | 0
Depreciation and amortization | 57 | 48 | 115 | 94
Total operating expenses | 10,692 | 10,444 | 21,755 | 21,205
Interest expense | 607 | 514 | 977 | 655
Interest expense | 0 | 0 | 0 | 0
Income (loss) before income taxes | 607 | 514 | 977 | 655
Operating Segments | Group and Specialty |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 1,673 | 1,683 | 3,373 | 3,343
Services | 143 | 176 | 304 | 353
Revenues | 1,816 | 1,859 | 3,677 | 3,696
Investment income | 7 | 6 | 18 | 12
Total revenues | 1,828 | 1,871 | 3,705 | 3,720
Benefits | 1,312 | 1,302 | 2,598 | 2,524
Operating costs | 394 | 423 | 793 | 857
Merger termination fee and related costs, net |  | 0 | 0 | 0
Depreciation and amortization | 21 | 22 | 42 | 43
Total operating expenses | 1,727 | 1,747 | 3,433 | 3,424
Interest expense | 101 | 124 | 272 | 296
Interest expense | 0 | 0 | 0 | 0
Income (loss) before income taxes | 101 | 124 | 272 | 296
Operating Segments | Healthcare Services |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 0 | 0 | 0 | 0
Services | 83 | 81 | 171 | 160
Revenues | 83 | 81 | 171 | 160
Investment income | 8 | 7 | 16 | 14
Total revenues | 5,982 | 6,288 | 11,940 | 12,518
Benefits | 0 | 0 | 0 | 0
Operating costs | 5,677 | 5,974 | 11,357 | 11,916
Merger termination fee and related costs, net |  | 0 | 0 | 0
Depreciation and amortization | 35 | 35 | 69 | 71
Total operating expenses | 5,712 | 6,009 | 11,426 | 11,987
Interest expense | 270 | 279 | 514 | 531
Interest expense | 0 | 0 | 0 | 0
Income (loss) before income taxes | 270 | 279 | 514 | 531
Operating Segments | Individual Commercial |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 247 | 1,024 | 530 | 1,917
Services | 0 | 0 | 0 | 0
Revenues | 247 | 1,024 | 530 | 1,917
Investment income | 1 | 1 | 2 | 3
Total revenues | 248 | 1,025 | 532 | 1,920
Benefits | 86 | 1,089 | 242 | 1,818
Operating costs | 40 | 152 | 102 | 321
Merger termination fee and related costs, net |  | 0 | 0 | 0
Depreciation and amortization | 4 | 9 | 7 | 18
Total operating expenses | 130 | 1,250 | 351 | 2,157
Interest expense | 118 | (225) | 181 | (237)
Interest expense | 0 | 0 | 0 | 0
Income (loss) before income taxes | 118 | (225) | 181 | (237)
Operating Segments | Individual Medicare Advantage | Retail |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 8,282 | 8,050 | 16,658 | 16,077
Operating Segments | Individual Medicare Advantage | Group and Specialty |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 0 | 0 | 0 | 0
Operating Segments | Individual Medicare Advantage | Healthcare Services |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 0 | 0 | 0 | 0
Operating Segments | Individual Medicare Advantage | Individual Commercial |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 0 | 0 | 0 | 0
Operating Segments | Group Medicare Advantage | Retail |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 1,277 | 1,085 | 2,595 | 2,162
Operating Segments | Group Medicare Advantage | Group and Specialty |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 0 | 0 | 0 | 0
Operating Segments | Group Medicare Advantage | Healthcare Services |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 0 | 0 | 0 | 0
Operating Segments | Group Medicare Advantage | Individual Commercial |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 0 | 0 | 0 | 0
Operating Segments | Medicare stand-alone PDP | Retail |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 925 | 1,015 | 1,866 | 2,054
Operating Segments | Medicare stand-alone PDP | Group and Specialty |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 0 | 0 | 0 | 0
Operating Segments | Medicare stand-alone PDP | Healthcare Services |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 0 | 0 | 0 | 0
Operating Segments | Medicare stand-alone PDP | Individual Commercial |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 0 | 0 | 0 | 0
Operating Segments | Total Medicare | Retail |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 10,484 | 10,150 | 21,119 | 20,293
Operating Segments | Total Medicare | Group and Specialty |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 0 | 0 | 0 | 0
Operating Segments | Total Medicare | Healthcare Services |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 0 | 0 | 0 | 0
Operating Segments | Total Medicare | Individual Commercial |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 0 | 0 | 0 | 0
Operating Segments | Fully-insured | Retail |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 118 | 106 | 236 | 210
Operating Segments | Fully-insured | Group and Specialty |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 1,350 | 1,357 | 2,728 | 2,694
Operating Segments | Fully-insured | Healthcare Services |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 0 | 0 | 0 | 0
Operating Segments | Fully-insured | Individual Commercial |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 247 | 1,024 | 530 | 1,917
Operating Segments | Specialty | Retail |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 0 | 0 | 0 | 0
Operating Segments | Specialty | Group and Specialty |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 323 | 321 | 645 | 639
Operating Segments | Specialty | Healthcare Services |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 0 | 0 | 0 | 0
Operating Segments | Specialty | Individual Commercial |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 0 | 0 | 0 | 0
Operating Segments | Medicaid and other | Retail |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 671 | 678 | 1,324 | 1,308
Operating Segments | Medicaid and other | Group and Specialty |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 0 | 5 | 0 | 10
Operating Segments | Medicaid and other | Healthcare Services |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 0 | 0 | 0 | 0
Operating Segments | Medicaid and other | Individual Commercial |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 0 | 0 | 0 | 0
Operating Segments | Provider | Retail |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Services | 0 | 0 | 0 | 0
Operating Segments | Provider | Group and Specialty |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Services | 0 | 0 | 0 | 0
Operating Segments | Provider | Healthcare Services |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Services | 63 | 74 | 133 | 145
Operating Segments | Provider | Individual Commercial |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Services | 0 | 0 | 0 | 0
Operating Segments | ASO and other | Retail |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Services | 2 | 2 | 4 | 3
Operating Segments | ASO and other | Group and Specialty |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Services | 143 | 176 | 304 | 353
Operating Segments | ASO and other | Healthcare Services |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Services | 0 | 0 | 0 | 1
Operating Segments | ASO and other | Individual Commercial |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Services | 0 | 0 | 0 | 0
Operating Segments | Pharmacy | Retail |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Services | 0 | 0 | 0 | 0
Operating Segments | Pharmacy | Group and Specialty |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Services | 0 | 0 | 0 | 0
Operating Segments | Pharmacy | Healthcare Services |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Services | 20 | 7 | 38 | 14
Operating Segments | Pharmacy | Individual Commercial |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Services | 0 | 0 | 0 | 0
Other Businesses |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 10 | 9 | 19 | 19
Services | 2 | 3 | 4 | 6
Revenues | 12 | 12 | 23 | 25
Investment income | 21 | 16 | 42 | 31
Total revenues | 33 | 28 | 65 | 56
Benefits | 32 | 31 | 61 | 56
Operating costs | 2 | 4 | 6 | 8
Merger termination fee and related costs, net |  | 0 | 0 | 0
Depreciation and amortization | 0 | 0 | 0 | 0
Total operating expenses | 34 | 35 | 67 | 64
Interest expense | (1) | (7) | (2) | (8)
Interest expense | 0 | 0 | 0 | 0
Income (loss) before income taxes | (1) | (7) | (2) | (8)
Other Businesses | Individual Medicare Advantage |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 0 | 0 | 0 | 0
Other Businesses | Group Medicare Advantage |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 0 | 0 | 0 | 0
Other Businesses | Medicare stand-alone PDP |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 0 | 0 | 0 | 0
Other Businesses | Total Medicare |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 0 | 0 | 0 | 0
Other Businesses | Fully-insured |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 0 | 0 | 0 | 0
Other Businesses | Specialty |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 0 | 0 | 0 | 0
Other Businesses | Medicaid and other |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 10 | 9 | 19 | 19
Other Businesses | Provider |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Services | 0 | 0 | 0 | 0
Other Businesses | ASO and other |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Services | 2 | 3 | 4 | 6
Other Businesses | Pharmacy |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Services | 0 | 0 | 0 | 0
Eliminations/ Corporate |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 0 | 0 | 0 | 0
Services | 0 | 0 | 0 | 0
Revenues | 0 | 0 | 0 | 0
Investment income | 40 | 43 | 85 | 89
Total revenues | (5,856) | (6,163) | (11,678) | (12,267)
Benefits | (213) | (240) | (409) | (452)
Operating costs | (5,623) | (5,923) | (11,169) | (11,820)
Merger termination fee and related costs, net |  | 27 | (947) | 61
Depreciation and amortization | (25) | (25) | (49) | (49)
Total operating expenses | (5,861) | (6,161) | (12,574) | (12,260)
Interest expense | 5 | (2) | 896 | (7)
Interest expense | 58 | 47 | 107 | 94
Income (loss) before income taxes | (53) | (49) | 789 | (101)
Eliminations/ Corporate | Individual Medicare Advantage |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 0 | 0 | 0 | 0
Eliminations/ Corporate | Group Medicare Advantage |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 0 | 0 | 0 | 0
Eliminations/ Corporate | Medicare stand-alone PDP |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 0 | 0 | 0 | 0
Eliminations/ Corporate | Total Medicare |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 0 | 0 | 0 | 0
Eliminations/ Corporate | Fully-insured |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 0 | 0 | 0 | 0
Eliminations/ Corporate | Specialty |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 0 | 0 | 0 | 0
Eliminations/ Corporate | Medicaid and other |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Premiums | 0 | 0 | 0 | 0
Eliminations/ Corporate | Provider |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Services | 0 | 0 | 0 | 0
Eliminations/ Corporate | ASO and other |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Services | 0 | 0 | 0 | 0
Eliminations/ Corporate | Pharmacy |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Services | $ 0 | $ 0 | $ 0 | $ 0

X
- Definition Depreciation and amortization expense excluding depreciation and amortization primarily from the delivery of pharmacy services by our wholly-owned pharmacy business (included in our Healthcare Services segment) which has been reclassified to benefit expenses. + References No definition available. + Details
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- Definition The total amount of expense recognized during the period for future policy benefits, claims and claims adjustment costs, and for selling, general and administrative costs. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04.5,6,7) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 + Details
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- Definition Amount, after effect of policies assumed or ceded, of expense related to provision for policy benefits and costs incurred for health insurance contracts. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04.5) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 + Details
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- Definition Amount, after premiums ceded to other entities and premiums assumed by the entity, of premiums earned. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04.1) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.13(c)) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 235 -Section S99 -Paragraph 2 -Subparagraph (SX 210.12-17) -URI http://asc.fasb.org/extlink&oid=34713774&loc=d3e574992-122915 + Details
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