Stock-Based Compensation Stock Unit Activity - Stock Compensation Plan (Detail) - Stock Compensation Plan - $ / shares shares in Millions |
3 Months Ended | 6 Months Ended | 12 Months Ended | ||||
|---|---|---|---|---|---|---|---|
Mar. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
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| Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] | |||||||
| Unvested units, beginning of period (in shares) | 2.2 | 1.1 | 1.1 | 1.3 | |||
| Units granted (in shares) | 0.6 | 0.6 | 0.3 | 0.3 | |||
| Units vested (in shares) | (0.4) | (0.4) | (0.2) | (0.4) | |||
| Units forfeited (in shares) | (0.3) | (0.1) | (0.1) | ||||
| Units impact of conversion related to the Separation (in shares) | [1] | 1.2 | |||||
| Unvested units, end of period (in shares) | 2.4 | 2.2 | 2.2 | 1.1 | 1.1 | ||
| Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] | |||||||
| Unvested units, beginning of period (in dollars per share) | $ 39.20 | $ 72.24 | $ 61.75 | $ 50.94 | |||
| Units granted (in dollars per share) | 56.69 | $ 46.25 | 86.14 | 76.95 | |||
| Units exercised (in dollars per share) | 35.88 | 33.01 | 51.56 | 42.64 | |||
| Units canceled/forfeited (in dollars per share) | 39.59 | 64.58 | 55.94 | ||||
| Unvested units, end of period (in dollars per share) | $ 43.83 | $ 39.20 | $ 39.20 | $ 72.24 | $ 61.75 | ||
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