Dividends and Distribution Payable (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Dividends Payable [Line Items]
Dividends Payable, Amount Per Share	$ 1.740	$ 1.640	$ 1.600
Dividend Declared, Ordinary Income [Member]
Dividends Payable [Line Items]
Dividends Payable, Amount Per Share	$ 1.398	$ 1.372	$ 1.200
Dividend Declared, Return of Capital [Member]
Dividends Payable [Line Items]
Dividends Payable, Amount Per Share	$ 0.342	$ 0.268	$ 0.400