Ownership, Description of Business, and Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)	1 Months Ended		12 Months Ended
	May 31, 2015	May 31, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Aug. 12, 2015	Apr. 24, 2014
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Comprehensive income (loss) attributable to Encore Capital Group, Inc. stockholders			$ 29,481,000	$ (11,765,000)	$ 97,609,000
Debt issuance costs, net of amortization			$ 41,654,000	41,655,000
Stock repurchase program, authorized amount						$ 50,000,000.0	$ 50,000,000.0
Stock repurchased during period (in shares)	839,295	400,000
Stock repurchased during period (amount)	$ 33,200,000	$ 16,800,000		$ 33,185,000	$ 16,815,000
Employee stock options to purchase common shares, excluded from computation of diluted earnings per share			0	0	0
2017 Convertible Senior Notes [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Debt instrument, interest rate			3.00%
Convertible debt			$ 115,000,000
Initial conversion price (in dollars per share)			$ 31.56
2017 Convertible Senior Notes [Member] | Adjusted Debt Conversion Rate Following Hedge Transactions [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Initial conversion price (in dollars per share)			$ 60.00
2020 Convertible Senior Notes [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Debt instrument, interest rate			3.00%
Convertible debt			$ 172,500,000
Initial conversion price (in dollars per share)			$ 45.72
2020 Convertible Senior Notes [Member] | Adjusted Debt Conversion Rate Following Hedge Transactions [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Initial conversion price (in dollars per share)			$ 61.55
2021 Convertible Senior Notes [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Debt instrument, interest rate			2.875%
Convertible debt			$ 161,000,000
Initial conversion price (in dollars per share)			$ 59.39
2021 Convertible Senior Notes [Member] | Adjusted Debt Conversion Rate Following Hedge Transactions [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Initial conversion price (in dollars per share)			$ 83.14
Long-term Debt [Member] | Accounting Standards Update 2015-03 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Debt issuance costs, net of amortization				$ 41,700,000
Other Assets [Member] | Accounting Standards Update 2015-03 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Debt issuance costs, net of amortization				(41,700,000)
Restatement Adjustment [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Comprehensive income (loss) attributable to Encore Capital Group, Inc. stockholders				$ (3,400,000)	$ (3,500,000)