Property, plant and equipment, net (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Property, plant and equipment, net
Less: accumulated depreciation	$ (722,696,000)		$ (722,696,000)		$ (721,527,000)
Property, plant and equipment, net excluding construction in progress	307,827,000		307,827,000		325,516,000
Totals	321,047,000		321,047,000		332,046,000
Depreciation expense	16,300,000	16,500,000	32,900,000	33,100,000
Land and buildings
Property, plant and equipment, net
Property, plant and equipment, gross	65,282,000		65,282,000		66,704,000
Network and outside plant facilities
Property, plant and equipment, net
Property, plant and equipment, gross	904,711,000		904,711,000		897,140,000
Furniture, fixtures and equipment
Property, plant and equipment, net
Property, plant and equipment, gross	50,516,000		50,516,000		73,185,000
Assets under capital lease
Property, plant and equipment, net
Property, plant and equipment, gross	10,014,000		10,014,000		10,014,000
Construction in progress
Property, plant and equipment, net
Totals	$ 13,220,000		$ 13,220,000		$ 6,530,000