Risks and Uncertainties - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2014
Unusual Risk or Uncertainty [Line Items]
Cash collateral, percentage	103.00%
Percentage of cash collateral amount equal to face amount	109.00%
Cash collateral to be provided for letter of credit as of the filing date	$ 89,300
Letter of credit termination date	Nov. 04, 2019
Outstanding borrowing under Amended Credit Agreement	50,000
Credit Agreement [Member]
Unusual Risk or Uncertainty [Line Items]
Outstanding borrowing under Amended Credit Agreement	50,000
2014 [Member] | PEAKS Guarantee [Member] | Scenario Forecast [Member]
Unusual Risk or Uncertainty [Line Items]
Payments under PEAKS guarantee	163,239
2014 [Member] | 2009 RSA [Member] | Scenario Forecast [Member]
Unusual Risk or Uncertainty [Line Items]
Payments under Loan Program	8,176
2015 [Member] | PEAKS Guarantee [Member] | Scenario Forecast [Member]
Unusual Risk or Uncertainty [Line Items]
Payments under PEAKS guarantee	9,813
2015 [Member] | 2009 RSA [Member] | Scenario Forecast [Member]
Unusual Risk or Uncertainty [Line Items]
Payments under Loan Program	$ 14,730