Segments, Major Customers (Details) (Sales Revenue, Segment [Member], Customer Concentration Risk [Member])	3 Months Ended
Mar. 31, 2013	Mar. 31, 2012
AT&T [Member]
Concentration Risk [Line Items]
Entity-Wide Revenue, Major Customer, Percentage	10.20%
Verizon [Member]
Concentration Risk [Line Items]
Entity-Wide Revenue, Major Customer, Percentage	10.10%	12.20%

Percentage of revenue generated from a single external customer that accounts for 10 percent or more of an entity's revenues.

No definition available.

Name:	us-gaap_EntityWideRevenueMajorCustomerPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration