Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Total
Beginning balance at Dec. 31, 2016	$ 111	$ 35,453	$ 152,810		$ 188,374
Beginning balance, shares at Dec. 31, 2016	11,093,489
Restricted stock grants, net of forfeitures	$ 1	(1)
Restricted stock grants, net of forfeitures, shares	73,936
Stock-based compensation		8,569			8,569
Common stock dividends			(8,561)		(8,561)
Net income (loss)			27,107		27,107
Ending balance at Sep. 30, 2017	$ 112	44,021	171,356		215,489
Ending balance, shares at Sep. 30, 2017	11,167,425
Beginning balance at Dec. 31, 2017	$ 112	47,079	162,006		209,197
Beginning balance, shares at Dec. 31, 2017	11,167,425
Restricted stock grants, net of forfeitures	$ 1	(1)
Restricted stock grants, net of forfeitures, shares	121,365
Issuance of stock in connection with the acquisition of Capella Education Company	$ 103	1,236,858			1,236,961
Issuance of stock in connection with the acquisition of Capella Education Company (in shares)	10,263,775
Filing fee related to new stock issuance		(147)			(147)
Stock-based compensation		11,035			11,035
Exercise of stock options, net	$ 1	6,830			6,831
Exercise of stock options, net (in shares)	131,779
Issuance of restricted stock, net		(426)			(426)
Issuance of restricted stock, net (in shares)	23,255
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 at Sep. 30, 2018	$ 217	$ 1,301,228	106,907	$ (22)	1,408,330
Ending balance, shares at Sep. 30, 2018	21,707,599
Impact of adoption of new accounting standards | Accounting Standards Update 2014-09			$ (171)		$ (171)