Equity Affiliates - Additional Information (Details) $ in Millions |
Mar. 31, 2018
USD ($)
|
|---|---|
| Schedule of Equity Method Investments [Line Items] | |
| Equity method investments exceeding minimum value | $ 169 |
| Minimum [Member] | |
| Schedule of Equity Method Investments [Line Items] | |
| Equity method investments exceeding minimum value | $ 5 |