Marketable Securities and Other Investments (Details) - USD ($) $ in Thousands, shares in Millions	1 Months Ended	3 Months Ended	6 Months Ended
	Apr. 30, 2015	Jun. 30, 2015	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Marketable Securities and Other Investments (Textual)
Marketable securities		$ 24,251	$ 24,251		$ 90,235
Aggregate unrealized gain		7,700	7,700
Sale of common stock aggregate price			$ 59,318	$ 219
Subsequent Event [Member] | Supervalu Inc. [Member]
Marketable Securities and Other Investments (Textual)
Number of shares sold	6.4
Sale of common stock aggregate price	$ 58,600
Marketable securities, realized gain		$ 32,400