Investment in Receivable Portfolios, Net - Summary of Changes in Balance of Investment in Receivable Portfolios (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Investment in Receivables Portfolio [Roll Forward]
Balance, beginning of period				$ 2,890,613				$ 2,382,809	$ 2,890,613	$ 2,382,809	$ 2,440,669
Purchases of receivable portfolios									1,131,898	1,058,235	906,719
Transfer of portfolios											0
Disposals or transfers to held for sale									(12,456)	(13,188)
Gross collections	$ (483,582)	$ (498,843)	$ (496,093)	(489,102)	$ (437,603)	$ (442,996)	$ (446,182)	(440,863)	(1,967,620)	(1,767,644)	(1,685,604)
Put-backs and Recalls									(14,429)	(2,871)	(28,613)
Foreign currency adjustments									(98,718)	138,663	(196,977)
Revenue recognized									1,167,132	1,053,373	1,030,792
Portfolio (allowance) reversals, net									41,473	41,236	(84,177)
Reclassification from prior period									0
Balance, end of period	3,137,893				2,890,613				$ 3,137,893	$ 2,890,613	$ 2,382,809
Revenue as a percentage of collections									59.30%	59.60%	61.20%
Accrual Basis Portfolios
Investment in Receivables Portfolio [Roll Forward]
Balance, beginning of period				2,879,170				2,368,366	$ 2,879,170	$ 2,368,366	$ 2,436,054
Purchases of receivable portfolios									1,131,898	1,057,066	906,719
Transfer of portfolios											(13,076)
Disposals or transfers to held for sale									(10,852)	(12,695)
Gross collections									(1,832,539)	(1,613,351)	(1,538,663)
Put-backs and Recalls									(14,253)	(2,577)	(27,561)
Foreign currency adjustments									(98,298)	138,828	(196,842)
Revenue recognized									1,041,947	909,239	892,732
Portfolio (allowance) reversals, net									32,429	34,294	(90,997)
Reclassification from prior period									0
Balance, end of period	3,129,502				2,879,170				$ 3,129,502	$ 2,879,170	$ 2,368,366
Revenue as a percentage of collections									56.90%	56.40%	58.00%
Cost Recovery Portfolios
Investment in Receivables Portfolio [Roll Forward]
Balance, beginning of period				11,443				14,443	$ 11,443	$ 14,443	$ 4,615
Purchases of receivable portfolios									0	1,169	0
Transfer of portfolios											13,076
Disposals or transfers to held for sale									(1,604)	(493)
Gross collections									(1,826)	(3,511)	(2,102)
Put-backs and Recalls									0	0	(1,019)
Foreign currency adjustments									(420)	(165)	(127)
Revenue recognized									0	0	0
Portfolio (allowance) reversals, net									0	0	0
Reclassification from prior period									798
Balance, end of period	8,391				11,443				$ 8,391	$ 11,443	$ 14,443
Revenue as a percentage of collections									0.00%	0.00%	0.00%
Zero Basis Portfolios
Investment in Receivables Portfolio [Roll Forward]
Balance, beginning of period				$ 0				$ 0	$ 0	$ 0	$ 0
Purchases of receivable portfolios									0	0	0
Transfer of portfolios											0
Disposals or transfers to held for sale									0	0
Gross collections									(133,255)	(150,782)	(144,839)
Put-backs and Recalls									(176)	(294)	(33)
Foreign currency adjustments									0	0	(8)
Revenue recognized									125,185	144,134	138,060
Portfolio (allowance) reversals, net									9,044	6,942	6,820
Reclassification from prior period									(798)
Balance, end of period	$ 0				$ 0				$ 0	$ 0	$ 0
Revenue as a percentage of collections									93.90%	95.60%	95.30%