Income Taxes - Uncertain Tax Positions (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Liability for uncertain tax positions
Balance at the beginning of the period	$ 528,000	$ 486,000
Increases (decreases) due to current year positions	(2,000)	18,000
Increases due to interest	28,000	24,000
Balance at the end of the period	$ 554,000	$ 528,000