Fair Value Disclosures - Summary of valuation of financial instruments measured at fair value on recurring basis (Details) - Fair value on a recurring basis - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Quoted prices in active markets for identical assets (Level 1)
Assets:
Trading securities
Available-for-sale securities - equity securities	$ 259	$ 275
Significant other observable inputs (Level 2)
Assets:
Trading securities	$ 16,081	$ 16,491
Available-for-sale securities - equity securities
Significant unobservable inputs (Level 3)
Assets:
Trading securities
Available-for-sale securities - equity securities