Summary of Significant Accounting Policies - Adoption of ASU, Adjustment to Additional Paid-in Capital (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income statement data:
Operating income		$ 9	$ 67,677	$ 48,037
Net income		48,148	51,569	29,376
Net income attributable to Blucora, Inc.		$ 48,148	$ 50,634	$ 27,039
Net income per share attributable to Blucora, Inc.:
Basic (in USD per share)	[1]	$ 1.00	$ 0.94	$ 0.61
Weighted average shares outstanding:
Basic (in shares)	[1]	48,264	47,394	44,370
Wealth management services
Income statement data:
Cost of revenue		$ 352,081	$ 253,580	$ 235,859

[1] Net income per share for the year ended December 31, 2018 included the noncontrolling interest redemption impact discussed further in “Note 2—Summary of Significant Accounting Policies” and in “Note 17—Net Income Per Share.”