Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Allowance for doubtful accounts
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of year	$ 171	$ 161	$ 166
Addition charged to costs and expenses	10	0	0
Other additions (deductions)	0	(5)	(36)
Less deductions	0	0	0
Balance at end of year	161	166	202
Deferred tax asset valuation allowance
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of year	86,092	72,104	65,832
Addition charged to costs and expenses	0	0	0
Other additions (deductions)	13,988	6,272	9,258
Less deductions	0	0	0
Balance at end of year	$ 72,104	$ 65,832	$ 56,574