Acquisitions (Details 1) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Revenue	$ 105,985	$ 99,671	$ 102,311	$ 93,605	$ 93,892	$ 88,948	$ 86,034	$ 64,293	$ 401,572	$ 333,167	$ 259,926
Net income	6,137	6,183	5,984	4,384	5,940	4,619	4,711	2,590	22,688	17,860	12,732
Basic earnings per share	$ 0.32	$ 0.33	$ 0.32	$ 0.23	$ 0.32	$ 0.25	$ 0.25	$ 0.14	$ 1.20	$ 0.95	$ 0.68
Diluted earnings per share	$ 0.32	$ 0.32	$ 0.31	$ 0.23	$ 0.31	$ 0.24	$ 0.25	$ 0.14	$ 1.18	$ 0.94	$ 0.68
Rwd Technologies, Llc [Member]
Revenue										354,609	324,587
Net income										$ 18,605	$ 8,279
Basic earnings per share										$ 0.99	$ 0.44
Diluted earnings per share										$ 0.98	$ 0.44