CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - Unaudited (Parenthetical) (USD $)	3 Months Ended
	Mar. 31, 2012
Statement of Stockholder's Equity
Common dividends declared - per share (in dollars per share)	$ 0.52
Issuance of shares of common stock, common stock offering, net of expenses (in shares)	368,158
Issuance of shares of common stock, dividend reinvestment plan (in shares)	1,068
Withheld shares of common stock to satisfy tax withholding obligations in connection with the vesting of restricted stock (in shares)	17,927