Fair Value of Employee Stock Options Granted as Determined by Black-Scholes Valuation Model Assumptions (Detail) - $ / shares |
3 Months Ended | |
|---|---|---|
Jun. 30, 2017 |
Jun. 30, 2016 |
|
| Nonqualified Stock Options [Member] | ||
| Stockholders Equity Note [Line Items] | ||
| Risk-free interest rate | 2.15% | 1.66% |
| Expected volatility | 17.81% | 23.60% |
| Weighted-average fair value of options granted (usd per share) | $ 14.70 | $ 17.32 |
| Expected dividend yield | 2.89% | 2.94% |
| Expected life (in years) | 7 years 6 months | 7 years 6 months |
| Long-Term Incentive Performance Award | ||
| Stockholders Equity Note [Line Items] | ||
| Risk-free interest rate | 1.46% | 1.01% |
| Expected volatility | 16.59% | 16.45% |
| Weighted-average fair value of options granted (usd per share) | $ 119.29 | $ 135.57 |
| Expected dividend yield | 113.55% | 128.59% |
| X | ||||||||||
- Definition The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|
| X | ||||||||||
- Definition The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|
| X | ||||||||||
- Definition The risk-free interest rate assumption that is used in valuing an option on its own shares. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|
| X | ||||||||||
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. No definition available.
|
| X | ||||||||||
- Definition The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|
| X | ||||||||||
- Definition Expected term of share-based compensation awards, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|
| X | ||||||||||
- Details
|
| X | ||||||||||
- Details
|