Investment Securities Available for Sale (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Cost	$ 244,468	$ 254,837
Gross Unrealized Gains	45,079	94,885
Gross Unrealized Losses	(1,171)	(3,679)
Fair Value	288,376	346,043
Marketable equity securities
Schedule of Available-for-sale Securities [Line Items]
Cost	63,524	63,041
Gross Unrealized Gains	44,623	92,255
Gross Unrealized Losses	(1,171)	(1,104)
Fair Value	106,976	154,192
Mutual funds invested in fixed income securities
Schedule of Available-for-sale Securities [Line Items]
Cost	54,864	61,485
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	(1,659)
Fair Value	54,864	59,826
Marketable debt securities
Schedule of Available-for-sale Securities [Line Items]
Cost	126,080	130,311
Gross Unrealized Gains	456	2,630
Gross Unrealized Losses	0	(916)
Fair Value	$ 126,536	$ 132,025