Significant Accounting Policies - New Accounting Pronouncements (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016
ASU 2016-01 Recognition and Measurement of Financial Assets and Financial Liabilities
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Approximate equity securities and cost method investments in aggregate	$ 75
ASU 2017-07 Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Amount of net periodic benefit costs (benefits) that will no longer be included within operating expenses once ASU No. 2017-07 is adopted.	$ (32)	$ (52)

This amount represents the components of net periodic benefit costs (benefits) (such as interest, expected return on plan assets, prior service cost amortization and actuarial gain/loss) that no longer will be included within operating expense after adoption of ASU No. 2017-07.

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration