Investment Securities At Fair Value (Securities with Continuous Unrealized Losses) (Details) $ in Thousands	Dec. 31, 2017 USD ($)
Schedule of Available-for-sale Securities [Line Items]
In loss position for Less than 12 months, Fair Value	$ 20,006
In loss position for 12 months or more, Fair Value	0
Total Fair Value	20,006
In loss position for Less than 12 months, Unrealized Losses	(1,409)
In loss position for 12 months or more, Unrealized Losses	0
Total Unrealized Losses	(1,409)
Marketable equity securities
Schedule of Available-for-sale Securities [Line Items]
In loss position for Less than 12 months, Fair Value	9,523
In loss position for 12 months or more, Fair Value	0
Total Fair Value	9,523
In loss position for Less than 12 months, Unrealized Losses	(1,380)
In loss position for 12 months or more, Unrealized Losses	0
Total Unrealized Losses	(1,380)
Mutual funds invested in fixed-income securities
Schedule of Available-for-sale Securities [Line Items]
In loss position for Less than 12 months, Fair Value	10,483
In loss position for 12 months or more, Fair Value	0
Total Fair Value	10,483
In loss position for Less than 12 months, Unrealized Losses	(29)
In loss position for 12 months or more, Unrealized Losses	0
Total Unrealized Losses	$ (29)