Supplemental Balance Sheet Information (Details) (USD $)
Mar. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Other current assets      
Total other current assets $ 1,597,000,000 $ 1,298,000,000  
Investments      
Total investments 102,000,000 102,000,000  
Other assets      
Total other assets 1,338,000,000 1,554,000,000  
Other current liabilities      
Dividends payable   600,000,000 600,000,000
Total other current liabilities 2,239,000,000 2,918,000,000  
Other liabilities      
Total other liabilities $ 1,386,000,000 $ 1,555,000,000