Variable Interest Entities - Schedule of Carrying Value of Assets and Liabilities of PEAKS Trust (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Variable Interest Entity [Line Items]
Restricted cash	$ 5,675	$ 6,040	$ 5,974
Current portion of PEAKS Trust student loans	8,984	10,584	10,339
PEAKS Trust student loans, excluding current portion, less allowance for loan losses of $28,535, $42,353 and $42,931	65,938	80,292	84,272
Total assets	732,149	752,838	771,113
Current portion of PEAKS Trust senior debt	20,534	37,545	96,516
Other current liabilities	58,436	27,153	27,732
PEAKS Trust senior debt, excluding current portion	36,930	48,166	53,320
Total liabilities	580,518	610,766	645,185
PEAKS Trust [Member]
Variable Interest Entity [Line Items]
Restricted cash	1,365	1,556	1,450
Current portion of PEAKS Trust student loans	6,058	7,169	6,933
PEAKS Trust student loans, excluding current portion, less allowance for loan losses of $28,535, $42,353 and $42,931	49,002	59,902	60,479
Total assets	56,425	68,627	68,862
Current portion of PEAKS Trust senior debt	20,534	37,545	96,516
Other current liabilities	141	199	287
PEAKS Trust senior debt, excluding current portion	36,930	48,166	53,320
Total liabilities	$ 57,605	$ 85,910	$ 150,123