Unaudited Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income
Beginning balance at Dec. 31, 2017	$ 209,197	$ 112	$ 47,079	$ 162,006	$ 0
Beginning balance, shares at Dec. 31, 2017		11,167,425
Increase (Decrease) in Stockholders' Equity [Roll Forward]
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			(147)
Stock-based compensation	11,035		11,035
Exercise of stock options, net (in shares)		131,779
Exercise of stock options, net	6,831	$ 1	6,830
Issuance of restricted stock, net (in shares)		144,620
Issuance of restricted stock, net	(426)	$ 1	(427)
Common stock dividends	(16,802)			(16,802)
Unrealized losses on marketable securities, net of tax	(22)				(22)
Net income (loss)	(38,126)			(38,126)
Ending balance, shares at Sep. 30, 2018		21,707,599
Ending balance at Sep. 30, 2018	1,408,330	$ 217	1,301,228	106,907	(22)
Beginning balance at Jun. 30, 2018	223,840	$ 113	53,015	170,712	0
Beginning balance, shares at Jun. 30, 2018		11,306,527
Increase (Decrease) in Stockholders' Equity [Roll Forward]
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			(147)
Stock-based compensation	5,098		5,098
Exercise of stock options, net (in shares)		131,779
Exercise of stock options, net	6,831	$ 1	6,830
Issuance of restricted stock, net (in shares)		5,518
Issuance of restricted stock, net	(426)		(426)
Common stock dividends	(11,024)			(11,024)
Unrealized losses on marketable securities, net of tax	(22)				(22)
Net income (loss)	(52,781)			(52,781)
Ending balance, shares at Sep. 30, 2018		21,707,599
Ending balance at Sep. 30, 2018	1,408,330	$ 217	1,301,228	106,907	(22)
Beginning balance at Dec. 31, 2018	1,425,224	$ 217	1,306,653	118,322	32
Beginning balance, shares at Dec. 31, 2018		21,743,498
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	9,030		8,947	83
Exercise of stock options, net (in shares)		103,364
Exercise of stock options, net	(1,772)	$ 2	(1,774)
Issuance of restricted stock, net (in shares)		117,643
Issuance of restricted stock, net	(7,472)	$ 1	(7,473)
Common stock dividends	(33,367)			(33,367)
Unrealized losses on marketable securities, net of tax	415				415
Net income (loss)	52,601			52,601
Ending balance, shares at Sep. 30, 2019		21,964,505
Ending balance at Sep. 30, 2019	1,444,659	$ 220	1,306,353	137,639	447
Beginning balance at Jun. 30, 2019	1,437,876	$ 219	1,305,148	132,060	449
Beginning balance, shares at Jun. 30, 2019		21,948,563
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	3,021		3,021
Exercise of stock options, net (in shares)		12,795
Exercise of stock options, net	(1,564)	$ 1	(1,565)
Issuance of restricted stock, net (in shares)		3,147
Issuance of restricted stock, net	(251)		(251)
Common stock dividends	(11,113)			(11,113)
Unrealized losses on marketable securities, net of tax	(2)				(2)
Net income (loss)	16,692			16,692
Ending balance, shares at Sep. 30, 2019		21,964,505
Ending balance at Sep. 30, 2019	$ 1,444,659	$ 220	$ 1,306,353	$ 137,639	$ 447