Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	$ 167,845	$ 197,337
Restricted cash	47,524	46,012
Notes receivable, net	424,117	426,858
Lines-of-credit, notes payable, and receivable-backed notes payable	497,098	521,312
Junior subordinated debentures	70,677	70,384
Estimated Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	167,845	197,337
Restricted cash	47,524	46,012
Notes receivable, net	510,000	525,000
Lines-of-credit, notes payable, and receivable-backed notes payable	502,600	529,400
Junior subordinated debentures	$ 87,000	$ 88,500