Share-Based Payments - Amounts of compensation expense recognized under stock-based payment programs (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock compensation expense	$ 1,098	$ 618	$ 2,587	$ 905
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock compensation expense	42	49	59	88
Restricted Stock | Director
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock compensation expense	162	138	369	274
Restricted Stock | Employee
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock compensation expense	112	87	204	145
Restricted Stock Units (RSUs) | Employee
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock compensation expense	79	51	154	105
Stock Performance Awards | Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock compensation expense	$ 703	$ 293	$ 1,801	$ 293