Variable Interest Entities - Schedule of Carrying Value of Assets and Liabilities of PEAKS Trust (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Feb. 28, 2013	Dec. 31, 2012	Mar. 31, 2012
Variable Interest Entity [Line Items]
Restricted cash	$ 6,693		$ 3,478	$ 7,629
PEAKS Trust student loans, less allowance for loan losses of $0	7,282		0	0
PEAKS Trust student loans, excluding current portion, less allowance for loan losses of $0	105,007		0	0
Total assets	783,286	6,614	675,204	662,850
Current portion of PEAKS Trust senior debt	103,356		0	0
Other current liabilities	52,185	3,060	106,796	60,641
PEAKS Trust senior debt, excluding current portion	123,660		0	0
Total	674,601	46,114	549,439	571,349
PEAKS Trust Student Loans [Member]
Variable Interest Entity [Line Items]
Restricted cash	2,600	1,703
PEAKS Trust student loans, less allowance for loan losses of $0	7,282	7,282
PEAKS Trust student loans, excluding current portion, less allowance for loan losses of $0	105,007	104,834
Total assets	114,889	113,819
Current portion of PEAKS Trust senior debt	103,356	103,356
Other current liabilities	519	471
PEAKS Trust senior debt, excluding current portion	123,660	122,740
Total	$ 227,535	$ 226,567