Schedule II Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Changes in valuation and qualifying Accounts
Charged to Costs and Expenses	$ 574
Balance at the end of the period	574
Allowance for deferred tax asset
Changes in valuation and qualifying Accounts
Balance at the beginning of the period	116,541	$ 75,941	$ 59,540
Charged to Costs and Expenses	(29,024)	40,600	16,401
Balance at the end of the period	$ 87,517	$ 116,541	$ 75,941