Summary of Significant Accounting Policies (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 item	Jun. 30, 2012	Dec. 31, 2012
Principles of Consolidation
Equity method investments ownership, low end of range (as a percent)	20.00%		20.00%
Equity method investments ownership, high end of range (as a percent)	50.00%		50.00%
Cost method investments ownership, maximum (as a percent)	20.00%		20.00%
Inventory
Finished goods	$ 27,600,000		$ 27,600,000		$ 32,700,000
Supplies	20,300,000		20,300,000		16,600,000
Prepaid Expenses and Other Current Assets
Amounts receivable from customers in connection with billed and unbilled investigator fees, volunteer payments and other out-of-pocket pass-through costs	108,000,000		108,000,000		82,000,000
Impairment of Long-Lived Assets
Other-than-temporary impairment of equity investment	0	7,373,000	0	7,373,000
Goodwill and other intangible assets and impairment
Goodwill impairment charge	$ 0	$ 17,959,000	$ 0	$ 17,959,000
Number of reporting units at significant risk for impairment			0