Business Combinations - Additional Information (Detail)				0 Months Ended	3 Months Ended	9 Months Ended	0 Months Ended		3 Months Ended	9 Months Ended
	Sep. 30, 2014 USD ($)	Dec. 31, 2013 USD ($)	May 02, 2014 Tax Lien Portfolios [Member] USD ($)	Aug. 06, 2014 Atlantic Credit and Finance, Inc. [Member] USD ($)	Sep. 30, 2014 Atlantic Credit and Finance, Inc. [Member] USD ($)	Sep. 30, 2014 Atlantic Credit and Finance, Inc. [Member]	Feb. 07, 2014 Marlin Acquisition [Member] USD ($)	Feb. 07, 2014 Marlin Acquisition [Member] GBP (£)	Sep. 30, 2014 Marlin Acquisition [Member] USD ($)	Sep. 30, 2014 Marlin Acquisition [Member] USD ($)	Feb. 07, 2014 Marlin Acquisition [Member] USD ($)	Apr. 01, 2014 Grove Holdings [Member]
Business Acquisition [Line Items]
Business acquisition, date of acquisition						Aug. 06, 2014				Feb. 07, 2014
Business acquisition, cash paid				$ 196,104,000			$ 274,068,000	£ 166,800,000
Business acquisition, repayment of debt of acquired entity				126,100,000
Business combination, acquisition and integration costs					500,000				200,000	9,900,000
Revenue of acquiree included in statement of income					10,700,000
Net income of acquiree included in statement of income					2,600,000
Cash consideration used to repay Acquiree loans							73,700,000	44,800,000
Liabilities assumed							246,500,000	150,000,000
Goodwill	921,519,000	504,213,000									329,859,000
Percentage of equity interest acquired												68.20%
Acquisition of property tax portfolio			$ 43,000,000