Investments in Equity Securities (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Cost	$ 276,674	$ 308,175
Gross Unrealized, Gains	75,445	70,205
Gross Unrealized, Losses	(13,212)	(2,358)
Carrying and fair value of equity securities	338,907	376,022
Common stocks
Schedule of Available-for-sale Securities [Line Items]
Cost	195,705	222,671
Gross Unrealized, Gains	48,413	60,102
Gross Unrealized, Losses	(5,576)	(707)
Carrying and fair value of equity securities	238,542	282,066
Preferred stocks
Schedule of Available-for-sale Securities [Line Items]
Cost	80,969	85,504
Gross Unrealized, Gains	27,032	10,103
Gross Unrealized, Losses	(7,636)	(1,651)
Carrying and fair value of equity securities	$ 100,365	$ 93,956