Fair Value Measurements (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2014
Trading equity securities [Abstract]
SERP money market fund	$ 683	$ 532
SERP mutual funds	2,900	3,195
Preferred stocks	830	973
Trading debt securities [Abstract]
Corporate bonds	4,832	4,009
Municipal bonds	2,252	2,060
Floating rate notes	417	422
U.S. Treasury bills	400	622
Other	1,510	1,496
Derivative financial instruments	947	547
Total financial assets	14,771	13,856
Financial Liabilities [Abstract]
SERP liabilities	6,228	8,128
Total financial liabilities	6,228	8,128
Investments included in Level 1 were transferred to Level 2	387
Net unrealized gains (losses) incurred	115	(17)
Level 1 [Member]
Trading equity securities [Abstract]
SERP money market fund	683	532
SERP mutual funds	2,900	3,195
Preferred stocks	830	973
Trading debt securities [Abstract]
Corporate bonds	3,517	2,825
Municipal bonds	0	0
Floating rate notes	100	100
U.S. Treasury bills	400	622
Other	0	0
Derivative financial instruments	0	0
Total financial assets	8,430	8,247
Financial Liabilities [Abstract]
SERP liabilities	0	0
Total financial liabilities	0	0
Level 2 [Member]
Trading equity securities [Abstract]
SERP money market fund	0	0
SERP mutual funds	0	0
Preferred stocks		0
Trading debt securities [Abstract]
Corporate bonds	1,315	1,184
Municipal bonds	2,252	2,060
Floating rate notes	317	322
U.S. Treasury bills	0	0
Other	1,510	1,496
Derivative financial instruments	947	547
Total financial assets	6,341	5,609
Financial Liabilities [Abstract]
SERP liabilities	6,228	8,128
Total financial liabilities	$ 6,228	$ 8,128