Credit Agreement (Details) (USD $)	3 Months Ended		9 Months Ended			1 Months Ended		9 Months Ended	1 Months Ended	9 Months Ended	1 Months Ended		9 Months Ended	3 Months Ended		9 Months Ended			1 Months Ended												9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	May 31, 2013 Credit Agreement2013 [Member]	Sep. 30, 2014 Credit Agreement2013 [Member]	Sep. 30, 2014 Credit Agreement2011 [Member]	May 31, 2013 Minimum [Member] Credit Agreement2013 [Member]	Sep. 30, 2014 Minimum [Member] Credit Agreement2013 [Member] item	May 31, 2013 Maximum [Member] Credit Agreement2013 [Member]	May 31, 2013 London Interbank Offered Rate L I B O R [Member] Minimum [Member] Credit Agreement2013 [Member]	Sep. 30, 2014 Health Data Insights Inc [Member] Credit Agreement2011 [Member]	Sep. 30, 2014 Revolving Credit Facility [Member]	Sep. 30, 2013 Revolving Credit Facility [Member]	Sep. 30, 2014 Revolving Credit Facility [Member]	Sep. 30, 2013 Revolving Credit Facility [Member]	May 31, 2013 Revolving Credit Facility [Member] Credit Agreement2013 [Member]	May 31, 2013 Revolving Credit Facility [Member] Minimum [Member] Credit Agreement2013 [Member]	May 31, 2013 Revolving Credit Facility [Member] Maximum [Member] Credit Agreement2013 [Member]	May 31, 2013 Revolving Credit Facility [Member] London Interbank Offered Rate L I B O R [Member]	May 31, 2013 Revolving Credit Facility [Member] London Interbank Offered Rate L I B O R [Member] Maximum [Member] Credit Agreement2013 [Member]	May 31, 2013 Revolving Credit Facility [Member] Base rate	May 31, 2013 Revolving Credit Facility [Member] Prime rate	May 31, 2013 Revolving Credit Facility [Member] Federal Fund Rate [Member]	May 31, 2013 Revolving Credit Facility [Member] Federal Fund Rate [Member] Credit Agreement2013 [Member]	May 31, 2013 Revolving Credit Facility [Member] One Month London Interbank Offered Rate L I B O R [Member]	May 31, 2013 Revolving Credit Facility [Member] One Month London Interbank Offered Rate L I B O R [Member] Credit Agreement2013 [Member]	May 31, 2013 Revolving Credit Facility [Member] One Month London Interbank Offered Rate L I B O R [Member] Minimum [Member] Credit Agreement2013 [Member]	May 31, 2013 Revolving Credit Facility [Member] One Month London Interbank Offered Rate L I B O R [Member] Maximum [Member] Credit Agreement2013 [Member]	Sep. 30, 2013 Term loan
Credit agreement
Period of revolving credit facility						5 years							5 years
Principal borrowing capacity						$ 500,000,000												$ 500,000,000
Number of incremental term loan facilities that may be added										1
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
Consolidated leverage ratio before reduction											3.50
Maximum consolidated leverage ratio											3.25
Reduction period of maximum consolidated leverage ratio						4 years
Minimum interest coverage ratio						3.00
Interest rate of debts																					LIBOR multiplied by the statutory reserve rate		base rate	prime rate	federal funds effective rate		one-month LIBOR
Interest rate margin (as a percent)												1.50%										2.25%				0.50%			0.50%	1.25%
Rate added to reference rate and interest margin																												1.00%
Unused commitment fee on the revolving credit facility of the credit agreement (as a percent)																			0.375%	0.50%
Outstanding principal repaid				8,750,000				323,800,000								35,000,000	60,000,000														8,800,000
Proceeds from revolving credit facility																	4,000,000
Revolving credit facility	197,796,000		197,796,000		232,796,000									197,800,000		197,800,000
Unpaid interest paid			4,438,000	7,666,000				1,100,000
Loan origination fees							2,900,000
Interest expense														1,011,000	1,757,000	3,175,000	6,712,000
Commitment fees														380,000	255,000	1,085,000	548,000
Unamortized balance of deferred origination fees and debt issue costs	7,500,000		7,500,000		9,000,000
Amortization of deferred financing costs	$ 500,000	$ 200,000	$ 1,563,000	$ 2,556,000
Effective annualized interest rate of debt (as a percent)	2.00%		2.00%