Valuation and Qualifying Accounts (Details) - Tax valuation allowance - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Balance at beginning of fiscal period	$ 111,236	$ 166,844
Charges to costs and expenses	4,077	(55,608)
Charges to other accounts	0	0
Deductions	0	0
Balance at end of fiscal period	$ 115,313	$ 111,236