Stock-Based Compensation Plans - Changes in Company's Common Stock Price During Reporting Period (Detail) - Stock Based Compensation Expense [Member] - $ / shares |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2015 |
Jun. 30, 2014 |
Jun. 30, 2015 |
Jun. 30, 2014 |
|
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||||
| Common stock price at beginning of period | $ 37.48 | $ 17.84 | $ 33.25 | $ 14.90 |
| Common stock price at end of period | 46.14 | 25.51 | 46.14 | 25.51 |
| Increase in common stock price | $ 8.66 | $ 7.67 | $ 12.89 | $ 10.61 |
| X | ||||||||||
- Definition Increase decrease in common stock price. No definition available.
|
| 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 Price of a single share of a number of saleable stocks of a company. No definition available.
|
| X | ||||||||||
- Details
|