Restatement of Previously Issued Unaudited Financial Statements - Summary of Table Sets Forth the Effect of Consolidation and Correction of Errors of Condensed Consolidated Balance Sheet (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013		Feb. 28, 2013	Dec. 31, 2012	Mar. 31, 2012	Dec. 31, 2011
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents	$ 206,638			$ 243,465	$ 171,970	$ 223,849
Restricted cash	6,693			3,478	7,629
Accounts receivable, net	106,308			78,928	55,475
PEAKS Trust student loans, less allowance for loan losses	7,282			0	0
Deferred income taxes	71,301			44,547	12,566
Prepaid expenses and other current assets	19,189			16,162	17,832
Total current assets	417,411			386,580	380,278
PEAKS Trust student loans, excluding current portion, less allowance for loan losses	105,007			0	0
Deferred income taxes	45,024			57,471	34,563
Other assets	31,721			41,263	49,516
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
Total current liabilities	355,307			327,023	331,775
PEAKS Trust senior debt, excluding current portion	123,660			0	0
Other liabilities	45,634			82,416	64,574
Total	674,601		46,114	549,439	571,349
Capital surplus	194,629			197,113	186,262
Retained earnings	950,202			967,473	891,875
Total shareholders' equity	108,685			125,765	91,501	169,105
Total liabilities and shareholders' equity	783,286			675,204	662,850
As Previously Reported [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents	210,012			246,342	178,476
Restricted cash	719			601	1,123
Accounts receivable, net	104,077			77,313	54,411
PEAKS Trust student loans, less allowance for loan losses	0
Deferred income taxes	29,513
Prepaid expenses and other current assets	18,651
Total current assets	362,972			384,965	379,214
PEAKS Trust student loans, excluding current portion, less allowance for loan losses	0
Deferred income taxes	56,858			56,112	34,081
Other assets	39,033
Total assets	642,986			672,230	661,304
Current portion of PEAKS Trust senior debt	0
Other current liabilities	34,807			86,722	50,920
Total current liabilities	234,573			306,949	322,054
PEAKS Trust senior debt, excluding current portion	0
Other liabilities	100,138			98,327	72,629
Total	484,711			545,276	569,683
Capital surplus	204,219			206,703	194,027
Retained earnings	990,202			959,072	884,230
Total shareholders' equity	158,275			126,954	91,621
Total liabilities and shareholders' equity	642,986			672,230	661,304
Consolidation of PEAKS Trust [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents	0
Restricted cash	2,600
Accounts receivable, net	0
PEAKS Trust student loans, less allowance for loan losses	7,282
Deferred income taxes	41,788
Prepaid expenses and other current assets	0
Total current assets	51,670
PEAKS Trust student loans, excluding current portion, less allowance for loan losses	105,007
Deferred income taxes	(13,324)
Other assets	(7,312)	[1]
Total assets	136,041
Current portion of PEAKS Trust senior debt	103,356
Other current liabilities	(12,275)	[1]
Total current liabilities	91,081
PEAKS Trust senior debt, excluding current portion	123,660
Other liabilities	(30,129)	[1]
Total	184,312
Capital surplus	0
Retained earnings	(48,571)
Total shareholders' equity	(48,571)
Total liabilities and shareholders' equity	136,041
Other Adjustments [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents	(3,374)
Restricted cash	3,374
Accounts receivable, net	2,231
PEAKS Trust student loans, less allowance for loan losses	0
Deferred income taxes	0
Prepaid expenses and other current assets	538
Total current assets	2,769
PEAKS Trust student loans, excluding current portion, less allowance for loan losses	0
Deferred income taxes	1,490
Other assets	0
Total assets	4,259
Current portion of PEAKS Trust senior debt	0
Other current liabilities	29,653	[1]
Total current liabilities	29,653
PEAKS Trust senior debt, excluding current portion	0
Other liabilities	(24,375)	[1]
Total	5,578
Capital surplus	(9,590)
Retained earnings	8,571
Total shareholders' equity	(1,019)
Total liabilities and shareholders' equity	$ 4,259

[1] Includes amounts that were eliminated from our consolidated financial statements as a result of the Consolidation.