Marketable Securities (Narrative) (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Gain (Loss) on Investments [Line Items]
Maximum maturity of debt securities, years			5 years
Accumulated pre-tax unrealized gains for marketable securities	$ 57,000		$ 57,000
Accumulated pre-tax unrealized loss on marketable securities					$ 11,000
Proceeds from sales of available-for-sale marketable securities	625,000	$ 300,000	1,402,000	$ 716,000
Available-for-sale securities, gross realized gain (loss)	0	$ 0	0	$ 0
Cost	4,993,000		4,993,000		791,000
Debt securities unrealized gain position
Gain (Loss) on Investments [Line Items]
Fair value	11,500,000		11,500,000		2,300,000
Accumulated pre-tax unrealized gains for marketable securities	47,000		47,000		1,000
Debt securities unrealized loss position
Gain (Loss) on Investments [Line Items]
Fair value	$ 827,000		$ 827,000		11,000,000
Accumulated pre-tax unrealized loss on marketable securities					$ 23,000