Business Combinations - Pro Forma (Details) (USD $)	3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Mar. 31, 2012 Parent and ADAM, Combined [Member]	Mar. 31, 2011 Parent and ADAM, Combined [Member]	Jun. 30, 2012 Parent and ADAM, Combined [Member] Companies	Jun. 30, 2011 Parent and ADAM, Combined [Member]
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Business Acquisition, Pro Forma Revenue, Increase (Decrease)					$ 5,800,000
Number of companies included in pro forma information							3
Business Acquisition, Pro Forma Information
Revenue	47,716,000	42,267,000	91,543,000	82,317,000
Revenue, pro forma							98,216,000	92,399,000
Business Acquisition, Pro Forma Revenue, Increase (Decrease), Percentage							6.00%
Revenue, Net, Increase (Decrease)							9,200,000
Net income	18,067,000	22,348,000	33,752,000	37,512,000
Net income, pro forma					$ 32,820,000	$ 38,582,000
Basic EPS	$ 0.49	$ 0.57	$ 0.92	$ 0.97
Basic EPS, pro forma					$ 0.89	$ 0.97
Diluted EPS	$ 0.47	$ 0.53	$ 0.86	$ 0.90
Diluted EPS, pro forma					$ 0.83	$ 0.90
Revenue, Net, Increase (Decrease), Percentage							11.00%