Acquisitions (Pro Forma Results of Operations) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Business Acquisition [Line Items]
Total revenues	$ 241,945	$ 228,819	$ 207,984	$ 197,738	$ 198,360	$ 199,029	$ 192,020	$ 191,040	$ 876,486	$ 780,449	$ 624,576
Net income (loss) attributable to controlling interests and available to common stockholders	7,467	(8,408)	15,327	9,430	11,201	12,897	9,664	9,829	23,816	43,591	70,233
Net income per common share - basic	$ 0.16	$ (0.19)	$ 0.34	$ 0.21	$ 0.25	$ 0.29	$ 0.22	$ 0.22	$ 0.52	$ 0.97	$ 1.60
Net income per common share - diluted	$ 0.16	$ (0.19)	$ 0.33	$ 0.21	$ 0.25	$ 0.28	$ 0.21	$ 0.22	$ 0.52	$ 0.96	$ 1.58
Cardpoint Limited [Member]
Business Acquisition [Line Items]
Business Acquisition, Pro Forma Revenue									938,962	883,350
Business Acquisition, Pro Forma Net Income									$ 24,220	$ 42,670
Business Acquisition, Pro Forma Earnings Per Share, Basic									$ 0.53	$ 0.95
Business Acquisition, Pro Forma Earnings Per Share, Diluted									$ 0.53	$ 0.94