Investment in Securities (Schedule of the Fair Values of Securities with Unrealized Losses) (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
Investment [Line Items]
Estimated fair value, less than 12 months	$ 6,325	$ 101,792
Estimated fair value, 12 months or more	27,626	3,554
Estimated fair value, total	33,951	105,346
Unrealized losses, 12 months or more	11	2,661
Unrealized losses, less than 12 months	354	262
Unrealized losses, total	365	2,923
State and Political Subdivisions [Member]
Investment [Line Items]
Estimated fair value, less than 12 months	6,325	101,792
Estimated fair value, 12 months or more	27,626	3,554
Estimated fair value, total	33,951	105,346
Unrealized losses, 12 months or more	11	2,661
Unrealized losses, less than 12 months	354	262
Unrealized losses, total	365	2,923
Certificates Of Deposit [Member]
Investment [Line Items]
Estimated fair value, less than 12 months
Estimated fair value, 12 months or more
Estimated fair value, total
Unrealized losses, 12 months or more
Unrealized losses, less than 12 months
Unrealized losses, total