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Condensed Consolidating Financial Information (Condensed Consolidating Statement of Cash Flows) (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2018 | Jun. 30, 2017 | Jun. 30, 2018 | Jun. 30, 2017
Net Cash Provided by (Used in) Operating Activities [Abstract] |  |  |  |
Net cash provided by operating activities |  |  | $ 12,537 | $ 10,749
Investing Activities |  |  |  |
Net transactions with affiliates |  |  | 0 | 0
Capital expenditures | $ (2,250) | $ (2,327) | (4,223) | (4,405)
Cash paid for intangible assets | (511) | (386) | (930) | (771)
Acquisitions and construction of real estate properties |  |  | (104) | (250)
Construction of Universal Beijing Resort |  |  | (116) | (29)
Acquisitions, net of cash acquired |  |  | (88) | (398)
Proceeds from sales of investments |  |  | 113 | 57
Purchases of investments |  |  | (538) | (1,825)
Other |  |  | 580 | 214
Net cash provided by (used in) investing activities |  |  | (5,306) | (7,407)
Financing Activities |  |  |  |
Proceeds from (repayments of) short-term borrowings, net |  |  | 23 | (1,695)
Proceeds from borrowings |  |  | 4,279 | 8,963
Repurchases and repayments of debt |  |  | (4,347) | (4,967)
Repurchases of common stock under repurchase program and employee plans |  |  | (2,998) | (2,476)
Dividends paid |  |  | (1,616) | (1,404)
Purchase of Universal Studios Japan noncontrolling interests |  |  | 0 | (2,299)
Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock |  |  | (140) | (137)
Other |  |  | (161) | 80
Net cash provided by (used in) financing activities |  |  | (4,960) | (3,935)
Increase (decrease) in cash, cash equivalents and restricted cash |  |  | 2,271 | (593)
Cash, cash equivalents and restricted cash, beginning of period |  |  | 3,571 | 3,415
Cash, cash equivalents and restricted cash, end of period | 5,842 | 2,822 | 5,842 | 2,822
Elimination and Consolidation Adjustments [Member] |  |  |  |
Net Cash Provided by (Used in) Operating Activities [Abstract] |  |  |  |
Net cash provided by operating activities |  |  | 0 | 0
Investing Activities |  |  |  |
Net transactions with affiliates |  |  | 0 | 0
Capital expenditures |  |  | 0 | 0
Cash paid for intangible assets |  |  | 0 | 0
Acquisitions and construction of real estate properties |  |  | 0 | 0
Construction of Universal Beijing Resort |  |  | 0 | 0
Acquisitions, net of cash acquired |  |  | 0 | 0
Proceeds from sales of investments |  |  | 0 | 0
Purchases of investments |  |  | 0 | 0
Other |  |  | 0 | 0
Net cash provided by (used in) investing activities |  |  | 0 | 0
Financing Activities |  |  |  |
Proceeds from (repayments of) short-term borrowings, net |  |  | 0 | 0
Proceeds from borrowings |  |  | 0 | 0
Repurchases and repayments of debt |  |  | 0 | 0
Repurchases of common stock under repurchase program and employee plans |  |  | 0 | 0
Dividends paid |  |  | 0 | 0
Purchase of Universal Studios Japan noncontrolling interests |  |  |  | 0
Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock |  |  | 0 | 0
Other |  |  | 0 | 0
Net cash provided by (used in) financing activities |  |  | 0 | 0
Increase (decrease) in cash, cash equivalents and restricted cash |  |  | 0 | 0
Cash, cash equivalents and restricted cash, beginning of period |  |  | 0 | 0
Cash, cash equivalents and restricted cash, end of period | 0 | 0 | 0 | 0
Comcast Parent [Member] | Reportable Legal Entities [Member] |  |  |  |
Net Cash Provided by (Used in) Operating Activities [Abstract] |  |  |  |
Net cash provided by operating activities |  |  | (491) | (465)
Investing Activities |  |  |  |
Net transactions with affiliates |  |  | 4,096 | 2,559
Capital expenditures |  |  | (10) | (3)
Cash paid for intangible assets |  |  | (2) | (2)
Acquisitions and construction of real estate properties |  |  | (76) | (143)
Construction of Universal Beijing Resort |  |  | 0 | 0
Acquisitions, net of cash acquired |  |  | 0 | 0
Proceeds from sales of investments |  |  | 0 | 0
Purchases of investments |  |  | (28) | (20)
Other |  |  | 0 | 101
Net cash provided by (used in) investing activities |  |  | 3,980 | 2,492
Financing Activities |  |  |  |
Proceeds from (repayments of) short-term borrowings, net |  |  | (902) | (627)
Proceeds from borrowings |  |  | 3,973 | 3,500
Repurchases and repayments of debt |  |  | (1,900) | (1,000)
Repurchases of common stock under repurchase program and employee plans |  |  | (2,998) | (2,476)
Dividends paid |  |  | (1,616) | (1,404)
Purchase of Universal Studios Japan noncontrolling interests |  |  |  | 0
Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock |  |  | 0 | 0
Other |  |  | (46) | (20)
Net cash provided by (used in) financing activities |  |  | (3,489) | (2,027)
Increase (decrease) in cash, cash equivalents and restricted cash |  |  | 0 | 0
Cash, cash equivalents and restricted cash, beginning of period |  |  | 0 | 0
Cash, cash equivalents and restricted cash, end of period | 0 | 0 | 0 | 0
Non-Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member] |  |  |  |
Net Cash Provided by (Used in) Operating Activities [Abstract] |  |  |  |
Net cash provided by operating activities |  |  | 13,896 | 12,004
Investing Activities |  |  |  |
Net transactions with affiliates |  |  | (4,290) | (3,728)
Capital expenditures |  |  | (4,213) | (4,402)
Cash paid for intangible assets |  |  | (928) | (769)
Acquisitions and construction of real estate properties |  |  | (28) | (107)
Construction of Universal Beijing Resort |  |  | (116) | (29)
Acquisitions, net of cash acquired |  |  | (88) | (398)
Proceeds from sales of investments |  |  | 46 | 47
Purchases of investments |  |  | (480) | (1,748)
Other |  |  | 131 | 64
Net cash provided by (used in) investing activities |  |  | (9,966) | (11,070)
Financing Activities |  |  |  |
Proceeds from (repayments of) short-term borrowings, net |  |  | 925 | (1,068)
Proceeds from borrowings |  |  | 306 | 5,463
Repurchases and repayments of debt |  |  | (2,444) | (3,414)
Repurchases of common stock under repurchase program and employee plans |  |  | 0 | 0
Dividends paid |  |  | 0 | 0
Purchase of Universal Studios Japan noncontrolling interests |  |  |  | (2,299)
Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock |  |  | (140) | (137)
Other |  |  | (115) | 100
Net cash provided by (used in) financing activities |  |  | (1,468) | (1,355)
Increase (decrease) in cash, cash equivalents and restricted cash |  |  | 2,462 | (421)
Cash, cash equivalents and restricted cash, beginning of period |  |  | 3,075 | 2,933
Cash, cash equivalents and restricted cash, end of period | 5,537 | 2,512 | 5,537 | 2,512
Comcast Holdings [Member] | Subsidiary Issuer [Member] | Reportable Legal Entities [Member] |  |  |  |
Net Cash Provided by (Used in) Operating Activities [Abstract] |  |  |  |
Net cash provided by operating activities |  |  | 6 | 102
Investing Activities |  |  |  |
Net transactions with affiliates |  |  | (455) | (102)
Capital expenditures |  |  | 0 | 0
Cash paid for intangible assets |  |  | 0 | 0
Acquisitions and construction of real estate properties |  |  | 0 | 0
Construction of Universal Beijing Resort |  |  | 0 | 0
Acquisitions, net of cash acquired |  |  | 0 | 0
Proceeds from sales of investments |  |  | 0 | 0
Purchases of investments |  |  | 0 | 0
Other |  |  | 449 | 0
Net cash provided by (used in) investing activities |  |  | (6) | (102)
Financing Activities |  |  |  |
Proceeds from (repayments of) short-term borrowings, net |  |  | 0 | 0
Proceeds from borrowings |  |  | 0 | 0
Repurchases and repayments of debt |  |  | 0 | 0
Repurchases of common stock under repurchase program and employee plans |  |  | 0 | 0
Dividends paid |  |  | 0 | 0
Purchase of Universal Studios Japan noncontrolling interests |  |  |  | 0
Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock |  |  | 0 | 0
Other |  |  | 0 | 0
Net cash provided by (used in) financing activities |  |  | 0 | 0
Increase (decrease) in cash, cash equivalents and restricted cash |  |  | 0 | 0
Cash, cash equivalents and restricted cash, beginning of period |  |  | 0 | 0
Cash, cash equivalents and restricted cash, end of period | 0 | 0 | 0 | 0
CCCL Parent [Member] | Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member] |  |  |  |
Net Cash Provided by (Used in) Operating Activities [Abstract] |  |  |  |
Net cash provided by operating activities |  |  | (78) | (116)
Investing Activities |  |  |  |
Net transactions with affiliates |  |  | 78 | 666
Capital expenditures |  |  | 0 | 0
Cash paid for intangible assets |  |  | 0 | 0
Acquisitions and construction of real estate properties |  |  | 0 | 0
Construction of Universal Beijing Resort |  |  | 0 | 0
Acquisitions, net of cash acquired |  |  | 0 | 0
Proceeds from sales of investments |  |  | 0 | 0
Purchases of investments |  |  | 0 | 0
Other |  |  | 0 | 0
Net cash provided by (used in) investing activities |  |  | 78 | 666
Financing Activities |  |  |  |
Proceeds from (repayments of) short-term borrowings, net |  |  | 0 | 0
Proceeds from borrowings |  |  | 0 | 0
Repurchases and repayments of debt |  |  | 0 | (550)
Repurchases of common stock under repurchase program and employee plans |  |  | 0 | 0
Dividends paid |  |  | 0 | 0
Purchase of Universal Studios Japan noncontrolling interests |  |  |  | 0
Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock |  |  | 0 | 0
Other |  |  | 0 | 0
Net cash provided by (used in) financing activities |  |  | 0 | (550)
Increase (decrease) in cash, cash equivalents and restricted cash |  |  | 0 | 0
Cash, cash equivalents and restricted cash, beginning of period |  |  | 0 | 0
Cash, cash equivalents and restricted cash, end of period | 0 | 0 | 0 | 0
NBCUniversal Media Parent [Member] | Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member] |  |  |  |
Net Cash Provided by (Used in) Operating Activities [Abstract] |  |  |  |
Net cash provided by operating activities |  |  | (796) | (776)
Investing Activities |  |  |  |
Net transactions with affiliates |  |  | 571 | 605
Capital expenditures |  |  | 0 | 0
Cash paid for intangible assets |  |  | 0 | 0
Acquisitions and construction of real estate properties |  |  | 0 | 0
Construction of Universal Beijing Resort |  |  | 0 | 0
Acquisitions, net of cash acquired |  |  | 0 | 0
Proceeds from sales of investments |  |  | 67 | 10
Purchases of investments |  |  | (30) | (57)
Other |  |  | 0 | 49
Net cash provided by (used in) investing activities |  |  | 608 | 607
Financing Activities |  |  |  |
Proceeds from (repayments of) short-term borrowings, net |  |  | 0 | 0
Proceeds from borrowings |  |  | 0 | 0
Repurchases and repayments of debt |  |  | (3) | (3)
Repurchases of common stock under repurchase program and employee plans |  |  | 0 | 0
Dividends paid |  |  | 0 | 0
Purchase of Universal Studios Japan noncontrolling interests |  |  |  | 0
Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock |  |  | 0 | 0
Other |  |  | 0 | 0
Net cash provided by (used in) financing activities |  |  | (3) | (3)
Increase (decrease) in cash, cash equivalents and restricted cash |  |  | (191) | (172)
Cash, cash equivalents and restricted cash, beginning of period |  |  | 496 | 482
Cash, cash equivalents and restricted cash, end of period | $ 305 | $ 310 | $ 305 | $ 310

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