Commitments and Contingencies - Additional Information (Detail) - USD ($)									1 Months Ended			3 Months Ended						4 Months Ended	9 Months Ended				12 Months Ended
	Nov. 02, 2015	Oct. 28, 2015	Jun. 10, 2015	Jun. 08, 2015	Mar. 19, 2015	Nov. 12, 2014	Oct. 09, 2014	Mar. 26, 2012	Mar. 31, 2014	Jan. 31, 2014	Apr. 30, 2013	Dec. 31, 2015	Sep. 30, 2015		Dec. 31, 2014	Sep. 30, 2014		Sep. 30, 2015	Sep. 30, 2015		Sep. 30, 2014		Dec. 31, 2014	Dec. 31, 2013	Oct. 31, 2014	Feb. 28, 2013
Loss Contingencies [Line Items]
Face amount of surety bonds													$ 21,000,000					$ 21,000,000	$ 21,000,000
Letter of credit payable													82,001,000					82,001,000	$ 82,001,000
Letter of credit payable																									$ 79,708,000
Letter of credit termination date																			Nov. 04, 2019
Expected loss on litigations																			$ 29,900,000
Insurance Recoveries																			25,000,000
Payments under PEAK Guarantee																							$ 159,300,000
Payments on Behalf of Borrowers																							1,832,000
Collateral maintained with bank for education loan													8,600,000		$ 8,600,000	$ 8,600,000		8,600,000	8,600,000		$ 8,600,000		8,600,000
Increase in collateral maintained in restricted bank account																			2,600,000
Additional payments expected in 2018													74,427,000					74,427,000	74,427,000
Estimated regular payment made																			35,331,000
Offset amounts relating to guarantee obligations													0			0			0		0
Litigation settlement amount								$ 395,000
Other Current Liabilities [Member]
Loss Contingencies [Line Items]
Litigation reserve													29,900,000					29,900,000	29,900,000
Prepaid Expenses and Other Current Assets [Member]
Loss Contingencies [Line Items]
Insurance recoveries receivable													25,000,000					25,000,000	25,000,000
Subsequent Event [Member] | New York Securities Litigation [Member]
Loss Contingencies [Line Items]
Litigation settlement amount	$ (16,962,000)
Subsequent Event [Member] | Indiana Securities Litigation [Member]
Loss Contingencies [Line Items]
Litigation settlement amount	$ (12,538,000)
Subsequent Event [Member] | Gallien Litigation [Member]
Loss Contingencies [Line Items]
Litigation settlement amount		$ (400,000)
Percentage of net settlement amounts paid to settlement class members in the form of individual settlement payments		55.00%
Net settlement amounts paid in individual settlement payments		$ 204,000
Letter of Credit Issued to Insurers and Agencies [Member]
Loss Contingencies [Line Items]
Letter of credit payable													2,293,000					2,293,000	2,293,000
Revolving Note [Member]
Loss Contingencies [Line Items]
Credit facility outstanding, amount													8,200,000					8,200,000	8,200,000
Payable in 2018 through 2027 [Member]
Loss Contingencies [Line Items]
Estimated regular payment made																			98,255,000
Payable 2023 through 2027 [Member]
Loss Contingencies [Line Items]
Estimated regular payment made																			33,900,000
CUSO Program [Member]
Loss Contingencies [Line Items]
Principal amount for private education loans													141,000,000					141,000,000	141,000,000
PEAKS Guarantee [Member]
Loss Contingencies [Line Items]
Payments under PEAK Guarantee																			25,313,000		2,700,000		161,100,000
Future recovery of PEAKS guarantee payments													40,000,000					40,000,000	40,000,000
Payments under PEAK Guarantee with respect to Asset/Liability Ratio							$ 50,000,000				$ 60,340,000				64,900,000	51,700,000
Payments on Behalf of Borrowers										$ 1,800,000
PEAKS Guarantee [Member] | Letter Agreement [Member]
Loss Contingencies [Line Items]
Payments under PEAK Guarantee									$ 40,000,000
CUSO RSA [Member]
Loss Contingencies [Line Items]
Discharge Payments													0			0			9,253,000		0
Deferred payments													2,574,000					3,402,000	3,402,000
Recoveries of charged off loans not yet received													351,000					468,000	468,000		475,000		475,000
Net guarantee obligation payments													0			1,809,000			13,093,000		4,556,000
Recoveries of charged off loans received																156,000			521,000		156,000
Regular Payments													0	[1]		1,809,000	[2]		3,840,000	[3]	$ 4,556,000	[2]
PEAKS Senior Debt [Member]
Loss Contingencies [Line Items]
Outstanding balance													64,367,000					64,367,000	64,367,000							$ 257,533,000
Payments under PEAK Guarantee with respect to Asset/Liability Ratio															$ 64,900,000	51,700,000			25,313,000				156,600,000
PEAKS Senior Debt [Member] | Letter Agreement [Member]
Loss Contingencies [Line Items]
Payments under PEAK Guarantee									$ 40,000,000
Fourth Amendment [Member] | CUSO RSA [Member]
Loss Contingencies [Line Items]
Discharge Payments						$ 2,577,000
Fifth Amendment [Member] | CUSO RSA [Member]
Loss Contingencies [Line Items]
Discharge Payments					$ 2,709,000
Sixth Amendment [Member] | CUSO RSA [Member]
Loss Contingencies [Line Items]
Discharge Payments			$ 6,544,000
Accrued interest rate				12.50%
Reduction amount in Regular Payments			$ 2,000,000
Scenario, Forecast [Member] | CUSO RSA [Member]
Loss Contingencies [Line Items]
Deferred payments												$ 2,911,000
Recoveries of charged off loans not yet received												$ 311,000
Period From October One Two Thousand Fifteen Through December Thirty One Two Thousand Fifteen [Member] | PEAKS Guarantee [Member]
Loss Contingencies [Line Items]
Payments under PEAKS guarantee																			5,500,000
Year 2016 [Member] | PEAKS Guarantee [Member]
Loss Contingencies [Line Items]
Payments under PEAKS guarantee																			7,100,000
Year 2017 [Member] | PEAKS Guarantee [Member]
Loss Contingencies [Line Items]
Payments under PEAKS guarantee																			11,000
Year 2020 [Member] | PEAKS Guarantee [Member]
Loss Contingencies [Line Items]
Payments under PEAKS guarantee																			13,200,000
Year 2020 [Member] | PEAKS Senior Debt [Member] | PEAKS Guarantee [Member]
Loss Contingencies [Line Items]
Outstanding balance													56,300,000					56,300,000	56,300,000
Year 2015 [Member] | PEAKS Senior Debt [Member] | PEAKS Guarantee [Member]
Loss Contingencies [Line Items]
Outstanding balance													0					0	0
CUSO [Member]
Loss Contingencies [Line Items]
Recoveries of charged off loans not yet received													0			$ 0			0
Offset amounts relating to guarantee obligations																								$ 8,472,000
Amount of offset to repay													9,900,000					9,900,000	9,900,000
Recoveries from charged-off loans																			1,049,000
CUSO [Member] | CUSO RSA [Member]
Loss Contingencies [Line Items]
Net guarantee obligation payments																							9,139,000
Regular Payments																							7,028,000
Recoveries from charged-off loans																							466,000
Recoveries from charged-off loans																			779,000
CUSO [Member] | Fourth Amendment [Member] | CUSO RSA [Member]
Loss Contingencies [Line Items]
Discharge Payments																							$ 2,577,000
Minimum [Member]
Loss Contingencies [Line Items]
Estimated decrease in unrecognized tax benefits													0					0	0
Minimum [Member] | Payable 2018 through 2022 [Member]
Loss Contingencies [Line Items]
Estimated regular payment made																			14,250,000
Maximum [Member]
Loss Contingencies [Line Items]
Estimated decrease in unrecognized tax benefits													$ 10,100,000					$ 10,100,000	10,100,000
Maximum [Member] | Payable 2018 through 2022 [Member]
Loss Contingencies [Line Items]
Estimated regular payment made																			$ 17,000,000

[1] As described above, we deferred payment of $2,574 of Regular Payments, that otherwise would have been due during this period, to January 2016. In addition, the amount of the recoveries of charged-off loans received by the CUSO during this period that are due but have not been paid to us and that we expect to offset against these Regular Payments was $351.

[2] This amount is net of $156 of recoveries from charged-off loans owed to us that we offset against amounts owed by us under the CUSO RSA.

[3] This amount is net of $521 of recoveries from charged-off loans owed to us that we offset against amounts owed by us under the CUSO RSA. In addition, we deferred payment of $3,402 of Regular Payments, that otherwise would have been due during this period, to January 2016. We also expect to utilize the amount of recoveries of charged-off loans received by the CUSO during this period that has not been paid to us, which totaled approximately $468, to offset against amounts that we expect to pay under the CUSO RSA in January 2016.