CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Parentheticals) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Balance (in shares)	103,410,000	99,233,000	88,266,000
Grant of restricted stock (in shares)		13,000	13,000
Grant of restricted stock (in dollars per share)		$ 22.00	$ 20.00
Vesting of restricted stock, granted shares		68,000	112,000
Dividend reinvestment and stock purchase plan, shares	5,063,000	2,853,000	2,961,000
Dividend reinvestment plan (in dollars per share)	$ 22.11	$ 20.78	$ 20.45
Exercised options, shares			15,000
Exercised options per share			$ 6.12
Grant of stock as payment of directors fees (in shares)	9,000	8,000	7,000
Grant of stock as payment of directors fees (in dollars per share)	$ 22.17	$ 19.43	$ 20.07
Equity Shelf Program (in shares)	3,398,000	1,419,000	6,865,000
Equity Shelf Program, (in dollars per share)	$ 23.47	$ 22.61	$ 20.74
Issuance of common stock for acquisitions, shares			995,000
Issuance of common stock for acquisitions, (in dollars per share)			$ 19.80
Common stock repurchase, shares		183,000
Common stock repurchase, purchase price per share		$ 15.96
Common dividends, (in dollars per share)	$ 1.69	$ 1.55	$ 1.37
Preferred dividends paid (in dollars per share)		$ 0.74	$ 2.09
Balance (in shares)	112,393,000	103,410,000	99,233,000
Executives
Grant of restricted stock (in shares)	428,000
Vesting of restricted stock, granted shares	72,000
Directors
Grant of restricted stock (in shares)	13,000
Grant of restricted stock (in dollars per share)	$ 20.29