Credit Agreement (Details) (USD $)	3 Months Ended		6 Months Ended			1 Months Ended		6 Months Ended	1 Months Ended	6 Months Ended	1 Months Ended		6 Months Ended	3 Months Ended		6 Months Ended			1 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013	May 31, 2013 Credit Agreement2013 [Member]	Jun. 30, 2014 Credit Agreement2013 [Member]	Jun. 30, 2014 Credit Agreement2011 [Member]	May 31, 2013 Minimum [Member] Credit Agreement2013 [Member]	Jun. 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]	Jun. 30, 2014 Health Data Insights Inc [Member] Credit Agreement2011 [Member]	Jun. 30, 2014 Revolving Credit Facility [Member]	Jun. 30, 2013 Revolving Credit Facility [Member]	Jun. 30, 2014 Revolving Credit Facility [Member]	Jun. 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] Maximum [Member] Credit Agreement2013 [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] 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]
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						5 years
Minimum interest coverage ratio						3.00
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
Unpaid interest paid			2,538,000	4,308,000				1,100,000
Loan origination fees							2,900,000
Interest expense														1,000,000	2,294,000	2,164,000	4,955,000
Commitment fees														376,000	177,000	704,000	293,000
Unamortized balance of deferred origination fees and debt issue costs	8,000,000		8,000,000		9,000,000
Amortization of financing cost	$ 500,000	$ 1,500,000	$ 1,000,000	$ 2,300,000
Effective annualized interest rate of debt (as a percent)	2.00%		2.00%