Investments in Unconsolidated Investees (Balance Sheet Data) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Alliance-HNI, LLC and Subsidiaries [Member]
Schedule of financial data of unconsolidated investees, Balance Sheet Data
Current assets	$ 4,763	$ 5,246
Noncurrent assets	9,740	10,142
Current liabilities	2,312	3,026
Noncurrent liabilities	2,072	2,669
Austin Cyberknife, Llc [Member]
Schedule of financial data of unconsolidated investees, Balance Sheet Data
Current assets	1,600	2,150
Noncurrent assets	1,539	1,819
Current liabilities	594	732
Noncurrent liabilities	834	1,067
Unconsolidated Investees, Including Alliance-HNI, LLC and Subsidiaries and Austin Cyberknife [Member]
Schedule of financial data of unconsolidated investees, Balance Sheet Data
Current assets	6,814	7,843
Noncurrent assets	11,370	12,092
Current liabilities	2,981	3,828
Noncurrent liabilities	$ 2,910	$ 3,736