Investments in Equity Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Cost	$ 262,816	$ 165,192
Gross Unrealized, Gains	28,031	8,216
Gross Unrealized, Losses	(4,195)	(22,542)
Carrying and fair value of equity securities	286,652	150,866
Common stocks
Schedule of Available-for-sale Securities [Line Items]
Cost	136,868	56,462
Gross Unrealized, Gains	4,434	0
Gross Unrealized, Losses	(2,415)	(19,189)
Carrying and fair value of equity securities	138,887	37,273
Preferred stocks
Schedule of Available-for-sale Securities [Line Items]
Cost	125,948	108,730
Gross Unrealized, Gains	23,597	8,216
Gross Unrealized, Losses	(1,780)	(3,353)
Carrying and fair value of equity securities	$ 147,765	$ 113,593