Fair Value of Financial Instruments - Summary of recurring level III assets (Details) - Level III - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance, beginning of period	$ 1,653	$ 3,210	$ 1,020	$ 2,271
Realized and unrealized gains (loss) included in earnings	105	(391)	738	548
Balance, end of period	$ 1,758	$ 2,819	$ 1,758	$ 2,819