Schedule II - Valuation and Qualifying Accounts Deferred Tax Assets - (Details) - Valuation allowance for deferred tax assets - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Valuation allowance and reserves
Balance at Beginning of Period	$ 146,259	$ 42,504	$ 41,769
Tax Valuation Allowance Charged to Income Tax Provision	11,194	1,049	735
Tax Valuation Allowance Credited to Income Tax Provision	(64,535)
Charged to Other Accounts	33,788	102,706
Balance at End of Period	$ 126,706	$ 146,259	$ 42,504