Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income
Beginning balance (in shares) at Dec. 31, 2016		11,093,489
Beginning balance at Dec. 31, 2016	$ 188,374	$ 111	$ 35,453	$ 152,810
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Stock-based compensation	11,627		11,627
Issuance of restricted stock, net (in shares)		73,936
Issuance of restricted stock, net	0	$ 1	(1)
Common stock dividends	(11,416)			(11,416)
Net income (loss)	20,612			20,612
Unrealized gains on marketable securities, net of tax	0
Ending balance (in shares) at Dec. 31, 2017		11,167,425
Ending balance at Dec. 31, 2017	209,197	$ 112	47,079	162,006
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Stock-based compensation	14,994		14,994
Issuance of restricted stock, net (in shares)		155,874
Issuance of restricted stock, net	(776)	$ 1	(777)
Common stock dividends	(27,842)			(27,842)
Net income (loss)	(15,671)			(15,671)
Impact of adoption of new accounting standard | Accounting Standards Update 2014-09	(171)			(171)
Issuance of stock in connection with the acquisition of Capella Education Company (in shares)		10,263,775
Issuance of stock in connection with the acquisition of Capella Education Company	1,236,961	$ 103	1,236,858
Filing fee related to new stock issuance	(148)		(148)
Exercise of stock options, net (in shares)		156,424
Exercise of stock options, net	8,648	$ 1	8,647
Unrealized gains on marketable securities, net of tax	32				$ 32
Ending balance (in shares) at Dec. 31, 2018		21,743,498
Ending balance at Dec. 31, 2018	1,425,224	$ 217	1,306,653	118,322	32
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Stock-based compensation	12,116		12,033	83
Issuance of restricted stock, net (in shares)		117,947
Issuance of restricted stock, net	(7,472)	$ 1	(7,473)
Common stock dividends	(46,724)			(46,724)
Net income (loss)	81,138			81,138
Exercise of stock options, net (in shares)		103,364
Exercise of stock options, net	(1,773)	$ 2	(1,775)
Unrealized gains on marketable securities, net of tax	201				201
Ending balance (in shares) at Dec. 31, 2019		21,964,809
Ending balance at Dec. 31, 2019	$ 1,462,710	$ 220	$ 1,309,438	$ 152,819	$ 233