Other Income (Expense) - Summary (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Investment Income, Net [Abstract]
Interest and dividend income	$ 6,602	$ 6,940	$ 6,258
Accretion income	1,829	1,526	1,455
Realized gains (losses) on the sale of investments	795	5,311	(833)
Other-than-temporary impairment losses	0	0	(1,295)
Total net investment income from available-for-sale securities	9,226	13,777	5,585
Interest income from investments in SPEs	8,202	8,217	6,116
Interest accrued on notes receivable and other interest	348	694	990
Total investment income, net	17,776	22,688	12,691
Interest expense
Interest expense and amortization of discount and issuance costs for Senior Notes issued by SPE	(8,833)	(8,755)	(6,584)
Interest expense	(3,462)	(2,674)	(2,024)
Total interest expense	(12,295)	(11,429)	(8,608)
Claim settlement	12,548	0	0
Other income (expense), net
SEC investigation fees and expenses	742	(8,161)	0
Accretion income from retained interest investments	991	913	889
Hunting lease income	553	562	764
Litigation and insurance proceeds received	0	0	1,814
Other income, net	336	399	1,021
Other income (expense), net	2,622	(6,287)	4,488
Total other income, net	$ 20,651	$ 4,972	$ 8,571