Investment in Receivable Portfolios, Net - Additional Information (Detail) - USD ($)	3 Months Ended						6 Months Ended	9 Months Ended
	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Jun. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2013
Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Carrying Amount Net [Line Items]
Collection forecast estimated on receivable portfolios				120 months				120 months
Income recognized under cost recovery method								$ 0
Purchase price of receivable portfolios	$ 187,180,000			$ 299,509,000				731,114,000	$ 992,836,000
Face value of receivable portfolios	$ 2,100,000,000			$ 4,000,000,000				$ 8,700,000,000	$ 11,300,000,000
Purchase cost as a percentage of face value	9.00%			7.50%				8.40%	8.80%
Estimated future collections at acquisition for receivable portfolios	$ 336,400,000			$ 606,300,000				$ 1,300,000,000	$ 2,000,000,000
Revenue recognized, net	265,523,000	$ 270,301,000	$ 264,110,000	251,785,000	$ 248,231,000	$ 237,568,000		799,934,000	737,584,000
Portfolio allowance	71,715,000	68,454,000		80,625,000	86,428,000		$ 86,428,000	71,715,000	80,625,000	$ 75,673,000	$ 93,080,000
Estimate of Zero Basis Cash Flows [Member]
Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Carrying Amount Net [Line Items]
Revenue recognized, net	31,843,000	$ 26,876,000	$ 15,571,000	$ 7,224,000	$ 6,708,000	$ 6,511,000		74,300,000	$ 20,400,000
Consent order, Consumer Finance Protection Bureau [Member]
Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Carrying Amount Net [Line Items]
CFPB settlement of future cash flows	22,200,000							22,200,000
Portfolio allowance	8,300,000							8,300,000
Hillesden Securities Ltd (dlc) [Member]
Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Carrying Amount Net [Line Items]
Investment in receivable portfolios	216,000,000							216,000,000
Marlin [Member]
Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Carrying Amount Net [Line Items]
Investment in receivable portfolios	208,500,000							208,500,000
Atlantic Credit and Finance, Inc. [Member]
Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Carrying Amount Net [Line Items]
Investment in receivable portfolios	$ 105,400,000							$ 105,400,000
Minimum [Member]
Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Carrying Amount Net [Line Items]
Collection forecast estimated on receivable portfolios							84 months
Maximum [Member]
Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Carrying Amount Net [Line Items]
Collection forecast estimated on receivable portfolios							96 months