Segment Reporting - Reconciliation of Operating Profit (Loss) from Segments to Consolidated (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Reconciliation of income from continuing operations from segments to consolidated [Abstract]
Total consolidated operating income (loss)	$ 18,698	$ 8,252	$ 33,046	$ 18,925
Interest expense	(8,851)	(9,389)	(18,183)	(18,489)
Gain (loss) on investments, net	56	73	24	193
Non-operating income (loss), net	783	1,224	1,804	2,479
Income (loss) before income taxes	$ 10,686	$ 160	$ 16,691	$ 3,108