Share-Based Compensation - Components of Share Based Compensation Awards (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]
Pre-tax compensation expense	$ 436	$ 360	$ 810	$ 686
Income tax benefit	(115)	(114)	(234)	(220)
Share-based compensation expense, net of income taxes	321	246	576	466
Stock and ESPP Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Pre-tax compensation expense	50	80	88	126
Income tax benefit	20	(2)	18	(2)
Share-based compensation expense, net of income taxes	70	78	106	124
Restricted Stock Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Pre-tax compensation expense	386	280	722	560
Income tax benefit	(135)	(112)	(252)	(218)
Share-based compensation expense, net of income taxes	$ 251	$ 168	$ 470	$ 342