Schedule II - Valuation and Qualifying Accounts (Details) - Allowance for doubtful accounts - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Activity in Provision for Doubtful Accounts
Balance at the Beginning of the Period	$ 0	$ 0	$ 0
Charged to Revenue, Cost or Expense	22	993	213
Deduction	(22)	(993)	(213)
Balance at the End of the Period	$ 0	$ 0	$ 0