Schedule II - Valuation and Qualifying Accounts - Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Balance at Beginning of Period	$ 80,505
Balance at End of Period	87,626	$ 80,505
Valuation Allowance of Deferred Tax Assets [Member]
Balance at Beginning of Period	80,505	71,939	$ 65,272
Additions Charged to Costs and Expenses	7,121	8,566	6,667
Additions Charged to Other Accounts
Deductions
Balance at End of Period	$ 87,626	$ 80,505	$ 71,939