Discontinued Operations- Income Statement and Balance Sheet (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Major classes of items in net income (loss):
Discontinued operation, revenues	$ 0	$ 227,989	$ 352,077
Discontinued operation, operating expenses	0	(211,395)	(391,702)
Discontinued operation, other loss, net	0	(719)	(2,673)
Income (loss) from discontinued operations before income taxes	0	15,875	(42,298)
Loss on sale of discontinued operations before income taxes	0	(73,800)	0
Discontinued operation, income (loss) from discontinued operation, before income taxes	0	(57,925)	(42,298)
Discontinued operation, income tax benefit (expense)	0	(5,196)	14,950
Discontinued operations, net of income taxes	$ 0	$ (63,121)	$ (27,348)