Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for receivables from related parties
Balance at beginning of fiscal period	$ 0	$ 370	$ 400
Charges to costs and expenses	0	0	0
Charges to other accounts	0	0	0
Deductions	0	(370)	(30)
Balance at end of fiscal period	0	0	370
Tax valuation allowance
Balance at beginning of fiscal period	166,844	161,160	156,671
Charges to costs and expenses	(55,608)	0	0
Charges to other accounts	0	5,684	4,489
Deductions	0	0	0
Balance at end of fiscal period	$ 11,236	$ 166,844	$ 161,160