Investment in Receivable Portfolios, Net - Investment in Receivable Portfolios (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Sep. 30, 2018	Sep. 30, 2017
Investment in Receivables Portfolio [Roll Forward]
Balance, beginning of period	$ 3,084,621		$ 2,890,613	$ 2,555,925		$ 2,382,809	$ 2,890,613	$ 2,382,809
Purchases of receivable portfolios	248,691			292,332			885,033	757,474
Disposals or transfers to assets held for sale	(5,364)			(3,801)			(10,731)	(11,269)
Gross collections	(498,843)			(442,996)			(1,484,038)	(1,330,041)
Put-Backs and Recalls	(2,074)			(649)			(14,402)	(5,676)
Foreign currency adjustments	(17,301)			44,412			(57,859)	127,720
Revenue recognized	295,357	$ 292,662	281,009	264,024	$ 263,407	249,838	869,028	777,269
Reclassification adjustments							0
Portfolio allowance reversals, net	4,029	17,632	9,811	19,564	8,829	2,132	31,472	30,525
Balance, end of period	$ 3,109,116	3,084,621		$ 2,728,811	2,555,925		$ 3,109,116	$ 2,728,811
Revenue as a percentage of collections	59.20%			59.60%			58.60%	58.40%
Accrual Basis Portfolios
Investment in Receivables Portfolio [Roll Forward]
Balance, beginning of period	$ 3,074,292		2,879,170	$ 2,541,590		2,368,366	$ 2,879,170	$ 2,368,366
Purchases of receivable portfolios	248,691			292,332			885,033	756,305
Disposals or transfers to assets held for sale	(4,253)			(3,536)			(9,358)	(11,004)
Gross collections	(463,474)			(407,435)			(1,379,095)	(1,212,357)
Put-Backs and Recalls	(2,056)			(407)			(14,231)	(5,401)
Foreign currency adjustments	(17,208)			44,366			(57,539)	127,852
Revenue recognized	263,109			230,403			771,628	665,818
Reclassification adjustments							0
Portfolio allowance reversals, net	1,196			17,817			24,689	25,551
Balance, end of period	$ 3,100,297	3,074,292		$ 2,715,130	2,541,590		$ 3,100,297	$ 2,715,130
Revenue as a percentage of collections	56.80%			56.50%			56.00%	54.90%
Cost Recovery Portfolios
Investment in Receivables Portfolio [Roll Forward]
Balance, beginning of period	$ 10,329		11,443	$ 14,335		14,443	$ 11,443	$ 14,443
Purchases of receivable portfolios	0			0			0	1,169
Disposals or transfers to assets held for sale	(1,111)			(265)			(1,373)	(265)
Gross collections	(306)			(435)			(1,729)	(1,534)
Put-Backs and Recalls	0			0			0	0
Foreign currency adjustments	(93)			46			(320)	(132)
Revenue recognized	0			0			0	0
Reclassification adjustments							798
Portfolio allowance reversals, net	0			0			0	0
Balance, end of period	$ 8,819	10,329		$ 13,681	14,335		$ 8,819	$ 13,681
Revenue as a percentage of collections	0.00%			0.00%			0.00%	0.00%
Zero Basis Portfolios
Investment in Receivables Portfolio [Roll Forward]
Balance, beginning of period	$ 0		$ 0	$ 0		$ 0	$ 0	$ 0
Purchases of receivable portfolios	0			0			0	0
Disposals or transfers to assets held for sale	0			0			0	0
Gross collections	(35,063)			(35,126)			(103,214)	(116,150)
Put-Backs and Recalls	(18)			(242)			(171)	(275)
Foreign currency adjustments	0			0			0	0
Revenue recognized	32,248			33,621			97,400	111,451
Reclassification adjustments							(798)
Portfolio allowance reversals, net	2,833			1,747			6,783	4,974
Balance, end of period	$ 0	$ 0		$ 0	$ 0		$ 0	$ 0
Revenue as a percentage of collections	92.00%			95.70%			94.40%	96.00%