Investments Financial Instrument Obligations (Details) (Total, USD $) In Thousands, unless otherwise specified	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Initial Obligation	$ 19,467
Estimated Fair Value	21,311
Corporate securities
Schedule of Available-for-sale Securities [Line Items]
Initial Obligation	666
Estimated Fair Value	621
Market indices
Schedule of Available-for-sale Securities [Line Items]
Initial Obligation	18,685
Estimated Fair Value	20,451
Covered call options
Schedule of Available-for-sale Securities [Line Items]
Initial Obligation	7
Estimated Fair Value	4
Naked put options
Schedule of Available-for-sale Securities [Line Items]
Initial Obligation	109
Estimated Fair Value	$ 235