Borrowings - Long-term Borrowings (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Long-term borrowings
Long-term borrowings	$ 119,529	$ 122,029
Non Recourse Revolving Bank Line of Credit [Member]
Long-term borrowings
Long-term borrowings	$ 75,030
Non Recourse Revolving Bank Line of Credit [Member] | LIBOR
Long-term borrowings
Variable rate basis	one-month LIBOR
Minimum | Non Recourse Revolving Bank Line of Credit [Member] | LIBOR
Long-term borrowings
Variable rate, basis spread (as a percent)	2.00%
Maximum | Non Recourse Revolving Bank Line of Credit [Member] | LIBOR
Long-term borrowings
Variable rate, basis spread (as a percent)	2.25%
Convertible Advances | FHLB Advances
Long-term borrowings
Long-term borrowings	$ 30,000
Fixed Rate Hybrid Advances | FHLB Advances
Long-term borrowings
Long-term borrowings	$ 14,500