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	Jun. 30, 2013	Mar. 31, 2013	Feb. 28, 2013	Dec. 31, 2012	Jun. 30, 2012	Mar. 26, 2012	Dec. 31, 2011
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents	$ 182,568	$ 206,638		$ 243,465	$ 161,198	$ 171,970	$ 223,849
Restricted cash	5,819			3,478	6,787
Accounts receivable, net	125,927			78,928	75,047
PEAKS Trust student loans, less allowance for loan losses	7,307			0	0
Deferred income taxes	68,215			44,547	16,859
Total current assets	409,851			386,580	274,462
PEAKS Trust student loans, excluding current portion, less allowance for loan losses	101,375			0	0
Deferred income taxes	45,267			57,471	36,654
Other assets	31,990			41,263	49,360
Total assets	767,578		6,614	675,204	558,651
Current portion of PEAKS Trust senior debt	102,695			0	0
Other current liabilities	43,177		3,060	106,796	33,091
Total current liabilities	349,701			327,023	261,452
PEAKS Trust senior debt, excluding current portion	124,983			0	0
Other liabilities	43,208			82,416	63,169
Total liabilities	637,892		46,114	549,439	474,621
Capital surplus	195,141			197,113	189,267
Retained earnings	970,405			967,473	935,145
Total shareholders' equity	129,686			125,765	84,030		169,105
Total liabilities and shareholders' equity	767,578			675,204	558,651
As Previously Reported [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents	185,408			246,342	167,234
Restricted cash	776			601	751
Accounts receivable, net	123,076			77,313	73,675
PEAKS Trust student loans, less allowance for loan losses	0
Deferred income taxes	29,131
Total current assets	358,179			384,965	273,090
PEAKS Trust student loans, excluding current portion, less allowance for loan losses	0
Deferred income taxes	52,759			56,112	36,016
Other assets	39,440
Total assets	629,473			672,230	556,641
Current portion of PEAKS Trust senior debt	0
Other current liabilities	41,521			86,722	19,454
Total current liabilities	245,350			306,949	247,815
PEAKS Trust senior debt, excluding current portion	0
Other liabilities	84,191			98,327	74,615
Total liabilities	449,541			545,276	472,430
Capital surplus	204,731			206,703	198,812
Retained earnings	1,011,061			959,072	925,781
Total shareholders' equity	179,932			126,954	84,211
Total liabilities and shareholders' equity	629,473			672,230	556,641
Consolidation of PEAKS Trust [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents	0
Restricted cash	2,203
Accounts receivable, net	0
PEAKS Trust student loans, less allowance for loan losses	7,307
Deferred income taxes	39,084
Total current assets	48,821
PEAKS Trust student loans, excluding current portion, less allowance for loan losses	101,375
Deferred income taxes	(8,981)
Other assets	(7,450)
Total assets	133,765
Current portion of PEAKS Trust senior debt	102,695
Other current liabilities	21,510
Total current liabilities	81,185
PEAKS Trust senior debt, excluding current portion	124,983
Other liabilities	(22,796)
Total liabilities	183,372
Capital surplus	0
Retained earnings	(49,607)
Total shareholders' equity	(49,607)
Total liabilities and shareholders' equity	133,765
Other Adjustments [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents	(2,840)
Restricted cash	2,840
Accounts receivable, net	2,851
PEAKS Trust student loans, less allowance for loan losses	0
Deferred income taxes	0
Total current assets	2,851
PEAKS Trust student loans, excluding current portion, less allowance for loan losses	0
Deferred income taxes	1,489
Other assets	0
Total assets	4,340
Current portion of PEAKS Trust senior debt	0
Other current liabilities	23,166
Total current liabilities	23,166
PEAKS Trust senior debt, excluding current portion	0
Other liabilities	(18,187)
Total liabilities	4,979
Capital surplus	(9,590)
Retained earnings	8,951
Total shareholders' equity	(639)
Total liabilities and shareholders' equity	$ 4,340