Net Income Per Share - Summary of Dilutive Effect for Awards with Exercise Price Less than Average Stock Price (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Numerator:
Net income (loss) attributable to Blucora, Inc.	$ (315,494)	$ 62,170
Denominator:
Weighted average common shares outstanding, basic (in shares)	47,827	48,161
Dilutive potential common shares (in shares)	0	1,381
Weighted average common shares outstanding, diluted (in shares)	47,827	49,542
Net income (loss) per share attributable to Blucora, Inc.:
Basic (in USD per share)	$ (6.60)	$ 1.29
Diluted (in USD per share)	$ (6.60)	$ 1.25
Shares excluded (in shares)	3,093	256