Variable Interest Entities - Schedule of Carrying Value of Assets and Liabilities of PEAKS Trust (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014
Variable Interest Entity [Line Items]
Restricted cash	$ 6,936	$ 6,040	$ 2,768
Current portion of PEAKS Trust student loans	9,379	10,584	7,420
PEAKS Trust student loans, excluding current portion, less allowance for loan losses of $36,921, $42,353 and $38,420	69,724	80,292	65,997
Total assets	711,300	749,160	776,219
Current portion of PEAKS Trust senior debt	23,068	37,545	132,429
Other current liabilities	27,288	27,050	46,233
PEAKS Trust senior debt, excluding current portion	31,007	38,658	58,442
Total liabilities	556,205	601,155	656,081
PEAKS Trust [Member]
Variable Interest Entity [Line Items]
Restricted cash	1,629	1,556	1,423
Current portion of PEAKS Trust student loans	6,250	7,169	7,420
PEAKS Trust student loans, excluding current portion, less allowance for loan losses of $36,921, $42,353 and $38,420	50,937	59,902	65,997
Total assets	58,816	68,627	74,840
Current portion of PEAKS Trust senior debt	23,068	37,545	132,429
Other current liabilities	158	199	395
PEAKS Trust senior debt, excluding current portion	31,007	38,658	58,442
Total liabilities	$ 54,233	$ 76,402	$ 191,266