Quarterly Financial Data (Tables)

12 Months Ended

Dec. 31, 2012

Quarterly Financial Data - Unaudited [Abstract]

Schedule of Quarterly Financial Information [Table Text Block]

	Quarter Ended
	March 31		June 30		Sept. 30		Dec. 31
2012
Total revenue	$	75,511	$	77,281	$	81,405	$	82,672
Gross profit	34,965		39,082		40,695		41,768
Net income	7,601		9,149		12,188		12,343
Net income per share:
Basic	$	0.54	$	0.65	$	0.85	$	0.86
Diluted	$	0.53	$	0.63	$	0.82	$	0.82
2011
Total revenue	$	71,471	$	77,796	$	76,458	$	76,470
Gross profit	34,626		36,201		35,574		35,953
Net income	8,073		9,493		9,261		17,842
Net income per share:
Basic	$	0.59	$	0.69	$	0.66	$	1.29
Diluted	$	0.57	$	0.67	$	0.65	$	1.26