Basic and Diluted Weighted Average Shares Outstanding (Detail) - shares	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Weighted Average Number of Shares Outstanding [Line Items]
Weighted average common shares	43,743,356	34,097,805	43,682,650	33,995,323
Dilutive common stock options and restricted stock units	480,561	437,427	433,961	433,483
Dilutive effect of convertible senior notes	791,802	559,582	578,134	286,991
Weighted average common shares, assuming dilution	45,015,720	35,094,814	44,694,745	34,715,797

Weighted Average Number of Shares Outstanding [Line Items]

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- Definition

Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of convertible debt securities using the if-converted method.

+ References

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-Publisher FASB
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-Topic 260
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- Definition

Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of share based payment arrangements using the treasury stock method.

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- Definition

The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period.

+ References

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Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period.

+ References

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