Business Acquisitions (Details 1) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Revenues	$ 40,246	$ 34,486	$ 114,467	$ 102,752
Net income	4,690	10,113	10,858	11,230
Net income attributable to common stockholders	$ 3,514	$ 8,902	$ 7,357	$ 8,228
Net income per share attributable to common stockholders - basic and diluted:	$ 0.05	$ 0.14	$ 0.11	$ 0.14
Weighted-average common shares outstanding:
Basic	64,518	64,009	64,446	59,044
Diluted	64,953	64,445	64,881	59,480