Goodwill and Other Intangible Assets (Details) (USD $)	3 Months Ended		12 Months Ended													12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012	Mar. 31, 2013 Customer Relationships	Dec. 31, 2012 Customer Relationships	Mar. 31, 2013 Supply agreement	Dec. 31, 2012 Supply agreement	Mar. 31, 2013 Technology databases	Dec. 31, 2012 Technology databases	Mar. 31, 2013 Non-compete agreements	Dec. 31, 2012 Non-compete agreements	Mar. 31, 2013 Favorable lease agreements	Dec. 31, 2012 Favorable lease agreements	Mar. 31, 2013 Trade Names	Dec. 31, 2012 Trade Names	Dec. 31, 2012 Medical Equipment Outsourcing	Mar. 31, 2013 Medical Equipment Outsourcing	Mar. 31, 2013 Technical and Professional Services	Dec. 31, 2012 Technical and Professional Services	Dec. 31, 2011 Technical and Professional Services	Mar. 31, 2013 Sales and Remarketing	Dec. 31, 2012 Sales and Remarketing	Dec. 31, 2011 Sales and Remarketing
Goodwill
Balance at the beginning of the period	$ 335,577,000	$ 325,911,000	$ 325,911,000													$ 251,653,000	$ 261,319,000	$ 55,655,000	$ 55,655,000	$ 55,655,000	$ 18,603,000	$ 18,603,000	$ 18,603,000
Acquisitions			9,666,000													9,666,000
Balance at the end of the period	335,577,000		335,577,000													261,319,000	261,319,000	55,655,000	55,655,000	55,655,000	18,603,000	18,603,000	18,603,000
Other intangible assets
Cost	149,862,000		149,862,000	115,731,000	115,731,000	26,000,000	26,000,000	7,217,000	7,217,000	780,000	780,000	134,000	134,000
Accumulated Amortization	(85,034,000)		(81,471,000)	(63,141,000)	(60,368,000)	(14,381,000)	(13,655,000)	(7,145,000)	(7,127,000)	(247,000)	(203,000)	(120,000)	(118,000)
Total	64,828,000		68,391,000	52,590,000	55,363,000	11,619,000	12,345,000	72,000	90,000	533,000	577,000	14,000	16,000
Cost	315,862,000		315,862,000
Net	230,828,000		234,391,000
Cost and net														166,000,000	166,000,000
Amortization	$ 3,600,000	$ 4,100,000