Valuation and Qualifying Accounts (Details) - Tax valuation allowance - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Balance at beginning of fiscal period	$ 115,313	$ 111,236
Charges to costs and expenses	2,412	4,077
Charges to other accounts	0	0
Deductions	0	0
Balance at end of fiscal period	$ 117,725	$ 115,313