Credit Agreement (Details) (USD $)	3 Months Ended	12 Months Ended	0 Months Ended	3 Months Ended	24 Months Ended	48 Months Ended	60 Months Ended	72 Months Ended		3 Months Ended		0 Months Ended					0 Months Ended				12 Months Ended		0 Months Ended	3 Months Ended			3 Months Ended			3 Months Ended
	Mar. 31, 2013	Dec. 31, 2011	May 03, 2013 Subsequent events	Mar. 31, 2013 Term loan	Dec. 31, 2012 Term loan	Dec. 31, 2014 Term loan	Dec. 31, 2015 Term loan	Dec. 31, 2016 Term loan	Dec. 31, 2011 Term loan Acquisition Health Data Insights, Inc	Mar. 31, 2013 Revolving credit loans	May 03, 2013 Revolving credit loans Subsequent events	May 03, 2013 Revolving credit loans Minimum Subsequent events	May 03, 2013 Revolving credit loans Maximum Subsequent events	May 03, 2013 Revolving credit loans LIBOR Rate Subsequent events	May 03, 2013 Revolving credit loans LIBOR Rate Minimum Subsequent events	May 03, 2013 Revolving credit loans LIBOR Rate Maximum Subsequent events	May 03, 2013 Revolving credit loans Federal funds rate Subsequent events	May 03, 2013 Revolving credit loans One-month LIBOR Rate Subsequent events	May 03, 2013 Revolving credit loans One-month LIBOR Rate Minimum Subsequent events	May 03, 2013 Revolving credit loans One-month LIBOR Rate Maximum Subsequent events	Dec. 31, 2011 Revolving credit loans Acquisition Health Data Insights, Inc	Mar. 31, 2013 Term loan and revolving credit facility	May 03, 2013 Term loan and revolving credit facility Subsequent events	Mar. 31, 2013 Term loan and revolving credit facility LIBOR Rate	Mar. 31, 2013 Term loan and revolving credit facility LIBOR Rate Minimum	Mar. 31, 2013 Term loan and revolving credit facility LIBOR Rate Maximum	Mar. 31, 2013 Term loan and revolving credit facility Base rate	Mar. 31, 2013 Term loan and revolving credit facility Base rate Minimum	Mar. 31, 2013 Term loan and revolving credit facility Base rate Maximum	Mar. 31, 2013 Term loan and revolving credit facility Prime rate	Mar. 31, 2013 Term loan and revolving credit facility Federal funds rate	Mar. 31, 2013 Term loan and revolving credit facility One-month LIBOR Rate
Debt
Period of revolving credit facility																					5 years		5 years
Principal amount of loan									$ 350,000,000
Principal borrowing capacity											500,000,000										100,000,000		500,000,000
Amount of revolving credit facility can be increased																					50,000,000
Interest rate of debts														LIBOR multiplied by a statutory reserve rate			Federal funds rate	one-month LIBOR						LIBOR multiplied by a statutory reserve rate			Base Rate			Prime Rate	Federal funds rate	One-month LIBOR
Interest rate margin															1.50%	2.25%	0.50%	1.00%	0.50%	1.25%					2.00%	3.00%		1.00%	2.00%		0.50%	1.00%
Interest rate at period end																						3.3125%
Effective annualized interest rate of debt (as a percent)				4.80%
Unused commitment fee on the revolving credit facility of the credit agreement (as a percent)										0.50%		0.375%	0.50%
Maximum consolidated leverage ratio before reduction	0.0400		3.5
Maximum consolidated leverage ratio	0.0350		3.25
Reduction period of maximum consolidated leverage ratio	2 years		2 years
Minimum interest coverage ratio	0.0300		3
Maximum amount of annual restricted payments that can be made under the Credit Agreement	30,000,000
Minimum consolidated leverage ratio	0.0300
Scheduled quarterly principal payments					4,400,000	8,800,000	21,800,000	43,800,000
Principal payments				26,300,000
Accrued interest expense				2,700,000
Commitment fees incurred										100,000
Loan origination fee and issuance costs incurred		12,700,000
Amortization period of deferred financing costs	5 years
Amortization of financing cost	900,000
Irrevocable letter of credit outstanding										$ 4,600,000