Shareholders' Equity And Net Income Per Share Dividends (Details) - USD ($) $ / shares in Units, $ in Millions |
3 Months Ended | 12 Months Ended | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Mar. 31, 2016 |
Dec. 31, 2015 |
Sep. 30, 2015 |
Jun. 30, 2015 |
Mar. 31, 2015 |
Dec. 31, 2014 |
Sep. 30, 2014 |
Jun. 30, 2014 |
Mar. 31, 2014 |
Dec. 31, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
Dec. 31, 2013 |
|
| Dividends Payable [Line Items] | |||||||||||||
| Cash dividends declared per share | $ 0.25 | $ 0.25 | $ 0.25 | $ 0.25 | $ 0.25 | $ 0.25 | $ 0.25 | $ 0.25 | $ 1 | $ 1 | $ 0.68 | ||
| Payments of Cash Dividends | $ 70 | $ 71 | $ 72 | $ 73 | $ 73 | $ 75 | $ 76 | $ 77 | $ 286 | $ 301 | |||
| Subsequent Event | |||||||||||||
| Dividends Payable [Line Items] | |||||||||||||
| Cash dividends declared per share | $ 0.29 | $ 1.16 | |||||||||||