Investment Securities Available for Sale (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Cost	$ 108,904	$ 106,649
Gross Unrealized Gain	73,726	67,348
Gross Unrealized Loss	(1,794)	(1,463)
Fair Value	180,836	172,534
Marketable equity securities
Schedule of Available-for-sale Securities [Line Items]
Cost	54,042	53,586
Gross Unrealized Gain	71,684	65,851
Gross Unrealized Loss	(1,335)	(963)
Fair Value	124,391	118,474
Marketable debt securities
Schedule of Available-for-sale Securities [Line Items]
Cost	54,862	53,063
Gross Unrealized Gain	2,042	1,497
Gross Unrealized Loss	(459)	(500)
Fair Value	$ 56,445	$ 54,060