XML 45 R34.htm IDEA: XBRL DOCUMENT v3.8.0.1
Valuation of Debt and Equity Investments and Certain Liabilities - Additional Information (Details) - USD ($)
3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Credit losses related to available-for-sale investments $ 0 $ 0  
Proceeds from sales, redemptions and maturities of short-term available-for-sale securities 1,455,000,000 $ 1,120,000,000  
Fair Value, Measurements, Recurring      
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Total assets fair value 4,086,000,000   $ 4,446,000,000
Total liabilities fair value 256,000,000   255,000,000
Fair Value, Measurements, Recurring | Level 3      
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Total assets fair value 0   0
Total liabilities fair value $ 0   $ 0