Credit Agreement (Details) (USD $)	3 Months Ended		6 Months Ended			6 Months Ended	3 Months Ended		6 Months Ended			1 Months Ended					1 Months Ended						1 Months Ended		1 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012	Jun. 30, 2013 Health Data Insights, Inc	Jun. 30, 2013 Revolving credit facility	Jun. 30, 2012 Revolving credit facility	Jun. 30, 2013 Revolving credit facility	Jun. 30, 2012 Revolving credit facility	May 31, 2013 Revolving credit facility	May 31, 2013 Revolving credit facility Minimum	May 31, 2013 Revolving credit facility Maximum	May 31, 2013 Revolving credit facility LIBOR Rate	May 31, 2013 Revolving credit facility LIBOR Rate Minimum	May 31, 2013 Revolving credit facility LIBOR Rate Maximum	May 31, 2013 Revolving credit facility Base rate	May 31, 2013 Revolving credit facility Prime rate	May 31, 2013 Revolving credit facility Federal funds rate	May 31, 2013 Revolving credit facility One-month LIBOR Rate	May 31, 2013 Revolving credit facility One-month LIBOR Rate Minimum	May 31, 2013 Revolving credit facility One-month LIBOR Rate Maximum	May 31, 2013 2013 Credit Agreement	Jun. 30, 2013 2013 Credit Agreement	May 31, 2013 2013 Credit Agreement Minimum	May 31, 2013 2013 Credit Agreement Maximum	Jun. 30, 2013 2011 Credit Agreement
Debt
Borrowing capacity											$ 500,000,000												$ 500,000,000
Period of revolving credit facility						5 years																	5 years
Amount of incremental credit facilities under specified circumstances																							75,000,000
Additional amount of incremental credit facilities under specified circumstances																									25,000,000
Secured leverage ratio																										2.5
Maximum consolidated leverage ratio before reduction																							3.50
Maximum consolidated leverage ratio																							3.25
Reduction period of maximum consolidated leverage ratio																							5 years
Minimum interest coverage ratio																							3.00
Interest rate margin (as a percent)															1.50%	2.25%			0.50%	1.00%	0.50%	1.25%
Interest rate of debts														LIBOR multiplied by a statutory reserve rate			Base Rate	Prime Rate	Federal funds rate	one-month LIBOR
Unused commitment fee on the revolving credit facility of the 2013 credit agreement (as a percent)												0.375%	0.50%
Outstanding principal repaid																											323,800,000
Unpaid interest paid			4,308,000	6,933,000																							1,100,000
Interest expense							2,300,000	3,100,000	5,000,000	6,100,000
Commitment fees	200,000	200,000	300,000	300,000
Loan origination fees																								2,900,000
Unamortized balance of deferred origination fees and debt issue costs	9,800,000		9,800,000		9,200,000
Amortization of interest expense related to our deferred origination fees and debt issue costs	1,500,000	900,000	2,300,000	1,900,000
Irrevocable letter of credit outstanding							$ 4,600,000		$ 4,600,000