Stock Purchase Plans (Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding and Exercisable) (Details) (USD $)	12 Months Ended
	Dec. 31, 2012
ESPP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options Outstanding and Exercisable	37,627
Weighted Average Exercise Price	$ 12.64
Weighted Average Remaining Life (years)	6 months
ISOP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options Outstanding and Exercisable	62,324
Weighted Average Exercise Price	$ 23.93
Weighted Average Remaining Life (years)	3 years 7 months 6 days
Price Range $16.11-$18.41 [Member] | ISOP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options Outstanding and Exercisable	10,700
Weighted Average Exercise Price	$ 16.11
Weighted Average Remaining Life (years)	6 years 2 months 12 days
Price Range $20.74-$23.05 [Member] | ISOP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options Outstanding and Exercisable	4,999
Weighted Average Exercise Price	$ 21.42
Weighted Average Remaining Life (years)	1 month 6 days
Price Range $23.05-$25.37 [Member] | ISOP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options Outstanding and Exercisable	20,425
Weighted Average Exercise Price	$ 24.04
Weighted Average Remaining Life (years)	4 years 8 months 12 days
Price Range $25.37-$27.68 [Member] | ISOP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options Outstanding and Exercisable	26,200
Weighted Average Exercise Price	$ 27.51
Weighted Average Remaining Life (years)	2 years 4 months 24 days