Investments (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Schedule of Available-for-sale Securities [Line Items]
Investments at fair value	$ 2,064	$ 2,160
Unrealized losses		132
Unrealized gains	191		187
Losses on sale of investments	66	27	8
Investments [Line Items]
Cost method investments	3,724	3,507
Equity method investments	2,426	2,638
Total other investments	6,150	6,145
Increase in cost method investments	221	190
Distributions from equity investments	812
Unrealized losses on investments	752
Gains from the difference between book value and trade in value	600	1,800
Purchase of investment securities	0	(84)	(127)
Dolphin Communications Fund II, L.P. [Member]
Investments [Line Items]
Gains from the difference between book value and trade in value	151
Burton Partnership [Member]
Investments [Line Items]
Equity method investments	2,086	1,708
Gains from the difference between book value and trade in value	379
Other [Member]
Investments [Line Items]
Equity method investments	340	930
NECA Services, Inc. [Member]
Investments [Line Items]
Cost method investments	505	505
CoBank [Member]
Investments [Line Items]
Cost method investments	2,968	2,747
Other [Member]
Investments [Line Items]
Cost method investments	251	255
Cash Management Trust [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments at fair value	0	197
Taxable Bond Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments at fair value	728	96
Domestic equity funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments at fair value	1,265	1,232
International Equity Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments at fair value	$ 71	$ 635