Segment Reporting - Reconciliation of Operating Profit (Loss) from Segments to Consolidated (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Reconciliation of income from continuing operations from segments to consolidated [Abstract]
Total consolidated operating income (loss)	$ 28,329	$ 9,475	$ 66,252	$ 28,400
Interest expense	(9,001)	(9,823)	(27,184)	(28,312)
Gain (loss) on investments, net	88	202	112	395
Non-operating income (loss), net	966	1,003	2,770	3,482
Income (loss) before income taxes	$ 20,382	$ 857	$ 41,950	$ 3,965