Summary of Stock Option Activity (Details) - Stock Options - USD ($)
$ / shares in Units, shares in Thousands, $ in Millions |
9 Months Ended |
12 Months Ended |
Sep. 30, 2016 |
Dec. 31, 2015 |
| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |
|
|
| Options outstanding as of January 1, 2016 |
1,187
|
|
| Granted |
341
|
|
| Forfeited or expired |
(49)
|
|
| Exercised |
(431)
|
|
| Options outstanding as of September 30, 2016 |
1,048
|
1,187
|
| Exercisable as of September 30, 2016 |
491
|
|
| Weighted Average Exercise Price (per share), Options outstanding at January 1, 2016 |
$ 39.70
|
|
| Weighted Average Exercise Price (per share), Granted |
65.26
|
|
| Weighted Average Exercise Price (per share), Forfeited or expired |
58.90
|
|
| Weighted Average Exercise Price (per share), Exercised |
32.85
|
|
| Weighted Average Exercise Price (per share), Options outstanding at September 30, 2016 |
49.96
|
$ 39.70
|
| Weighted Average Exercise Price (per share), Options exercisable at September 30, 2016 |
$ 40.26
|
|
| Weighted Average Remaining Life (years), Options outstanding |
4 years 4 months 24 days
|
3 years 10 months 24 days
|
| Weighted Average Remaining Life (years), Exercisable at September 30 , 2016 |
3 years
|
|
| Aggregate intrinsic Value, Options outstanding |
$ 26
|
$ 24
|
| Aggregate intrinsic Value, Exercisable at September 30, 2016 |
$ 17
|
|