Investments in Equity Securities (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Cost	$ 216,859	$ 203,627
Gross Unrealized, Gains	109,279	86,030
Gross Unrealized, Losses	(3,365)	(6,319)
Carrying and fair value of equity securities	322,773	283,338
Common stocks
Schedule of Available-for-sale Securities [Line Items]
Cost	119,043	118,536
Gross Unrealized, Gains	45,019	42,239
Gross Unrealized, Losses	0	0
Carrying and fair value of equity securities	164,062	160,775
Preferred stocks
Schedule of Available-for-sale Securities [Line Items]
Cost	97,816	85,091
Gross Unrealized, Gains	64,260	43,791
Gross Unrealized, Losses	(3,365)	(6,319)
Carrying and fair value of equity securities	$ 158,711	$ 122,563