CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY (Parenthetical) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Statement of Stockholder's Equity
Common dividends declared - per share (in dollars per share)	$ 2.0800	$ 2.0800	$ 2.0800
Issuance of shares of common stock, common stock offering, net of expenses (in shares)	586,977	0	1,600,000
Stock Issued During Period, Stock Options Exercised (in shares)	9,250	18,000	57,436
Issuance of shares of common stock, dividend reinvestment plan (in shares)	5,989	6,705	7,938
Withheld shares of common stock to satisfy tax withholding obligations in connection with the vesting of restricted stock (in shares)	3,564	19,668	8,514