Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Valuation Allowance of Deferred Tax Assets [Member]
Balance at Beginning of Period	$ 71,939	$ 65,272	$ 60,041
Additions Charged to Costs and Expenses	$ 8,566	$ 6,667	$ 5,231
Additions Charged to Other Accounts
Deductions
Balance at End of Period	$ 80,505	$ 71,939	$ 65,272
Balance at Beginning of Period	71,939
Balance at End of Period	$ 80,505	$ 71,939