Other Income (Expense) - Other Income (Expense) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Investment income, net
Interest and dividend income	$ 2,880	$ 4,548
Accretion income	221	922
Net realized (loss) gain on the sale of investments	(1,078)	3,122
Other-than-temporary impairment loss	(63)	(366)
Unrealized loss on investments, net	(538)	0
Interest income from investments in SPEs	2,050	2,051
Interest accrued on notes receivable and other interest	193	79
Total investment income, net	3,665	10,356
Interest expense
Interest expense and amortization of discount and issuance costs for Senior Notes issued by SPE	(2,196)	(2,193)
Other interest expense	(829)	(850)
Total interest expense	(3,025)	(3,043)
Other income, net
Accretion income from retained interest investments	290	263
Miscellaneous (expense) income, net	(13)	3,473
Other income, net	277	3,736
Total other income, net	$ 917	$ 11,049