Stock-Based Compensation (details) (USD $)	3 Months Ended
	Mar. 31, 2013
LTIP Paragraph 1 [Abstract]
Common stock was authorized for grants under the LTIP	37,300
Weighted-average per share grant date fair value of unvested shares	$ 38.96
Fair value pricing model LTIP	Monte-Carlo option pricing model
Stock price on valuation date	$ 45.38
Performance term (in years)	3 years 0 months 0 days
Quarterly Dividends Paid Per Share	$ 0.455
Expected dividend yield	3.90%
Dividend Discount Factor	0.8943
LTIP Paragraph 2 [Abstract]
Share Based Compensation Arrangement By Share Based Payment Award Grant Date LTIP & RSU	Feb. 27, 2013
Shares Granted Under RSU	25,748
Stock Price On Restricted Stock Unit Grant Date, Minimum	$ 45.38
SOP Paragraph 1 [Abstract]
Unrecognized compensation cost	$ 400,000.0
Unrecognized compensation cost, period for recognition	through 2014