Basic and Diluted Weighted Average Shares Outstanding (Detail) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Weighted Average Number of Shares Outstanding [Line Items]
Weighted average common shares	43,822,472	41,236,554	43,728,503	36,435,591
Dilutive common stock options and restricted stock units	651,265	484,242	511,433	454,340
Dilutive effect of convertible senior notes	1,354,438	842,206	892,179	496,402
Weighted average common shares, assuming dilution	45,828,175	42,563,002	45,132,115	37,386,333