Fair Value Measurements - Additional Information (Detail) $ in Thousands	1 Months Ended	12 Months Ended
	Oct. 31, 2015 acquisition	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of businesses acquired | acquisition	2
Increase (decrease) contingent consideration liability		$ (8,100)
Investment in receivable portfolios, net		$ 2,382,809	$ 2,440,669	$ 2,143,560	$ 1,590,249
Fluctuation in discount rate		1.00%
Convertible senior notes, carrying value		$ 448,500	448,500
Senior secured notes, carrying value		$ 11,320	28,750
UNITED STATES
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated market participant cost to collect		50.30%
Discount rate		10.50%
Increase or decrease of the fair value		$ 43,800
Europe [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated market participant cost to collect		29.90%
Discount rate		12.00%
Increase or decrease of the fair value		$ 52,000
Other Geographies [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated market participant cost to collect		32.80%
Discount rate		11.00%
Increase or decrease of the fair value		$ 6,400
Senior Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible senior notes, carrying value		416,500	406,600
Level 2 [Member] | Senior Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value estimate of convertible senior notes incorporates quoted market prices		431,700	372,200
Cabot Senior Secured Notes [Member] | Secured Debt [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Senior secured notes, carrying value		1,295,700	1,144,200
Cabot Senior Secured Notes [Member] | Level 2 [Member] | Secured Debt [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of senior notes		1,312,700	1,403,500
Estimate of Fair Value Measurement [Member] | Certain Loans Acquired in Transfer Not Accounted for as Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables fair value disclosure		2,446,600	2,473,800
Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration		2,531	10,403
Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration		2,531	10,403
Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration		$ 0	$ 0