Schedule II Valuation and Qualifying (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Valuation Allowance of Deferred Tax Assets
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	$ 12,847	$ 13,852	$ 27,087
Charged (Credited) to Expenses	13,925	(345)	(6,485)
Charged (Credited) to Other Accounts	5,260	(660)	(6,750)
Balance at End of Year	32,032	12,847	13,852
Allowance for Doubtful Accounts
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	0	0	0
Charged (Credited) to Expenses	2,404	0	0
Charged (Credited) to Other Accounts	(1,223)	0	0
Balance at End of Year	$ 1,181	$ 0	$ 0