Nature of Operations and Basis of Presentation (Details) - USD ($) $ in Millions |
3 Months Ended | 12 Months Ended | ||
|---|---|---|---|---|
Mar. 31, 2017 |
Mar. 31, 2016 |
Dec. 31, 2016 |
Dec. 31, 2015 |
|
| New Accounting Pronouncements or Change in Accounting Principle [Line Items] | ||||
| Equity investments not accounted for under the equity method of accounting | $ 528 | |||
| Interest income and other non-operating income, net | 161 | $ 85 | ||
| Decrease to Operating income | $ (2,745) | $ (1,972) | ||
| Accounting Standards Update 2017-07 [Member] | Pro Forma [Member] | ||||
| New Accounting Pronouncements or Change in Accounting Principle [Line Items] | ||||
| Interest income and other non-operating income, net | $ 1,200 | $ 380 | ||
| Decrease to Operating income | $ 1,200 | $ 380 | ||