Common stock (Nonemployee stock-based compensation) (Details) (USD $)	12 Months Ended				12 Months Ended				3 Months Ended	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Mar. 31, 2012	Dec. 31, 2013 Nonemployees	Dec. 31, 2012 Nonemployees	Dec. 31, 2011 Nonemployees	Dec. 31, 2010 2010 Revenue Performance [Member] Equity Option [Member] ExperiaHealth, Inc.	Mar. 31, 2012 2011 Revenue Performance [Member] Equity Option [Member] ExperiaHealth, Inc.	Dec. 31, 2010 2011 Revenue Performance [Member] Equity Option [Member] ExperiaHealth, Inc.
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 8,667,000	$ 4,232,000	$ 1,458,000		$ 0	$ 29,000	$ 907,000
Share-based for Nonemployee Services, Securities Issued			67,916					41,666		41,666
Nonemployee Shares Vested from Performance Award								35,452	41,666
Business Combination, Contingent Consideration, Liability			$ 419,000	$ 448,000