Equity (Details 2) - $ / shares								3 Months Ended									9 Months Ended
	Aug. 14, 2015	May. 15, 2015	Feb. 13, 2015	Nov. 17, 2014	Aug. 15, 2014	May. 15, 2014	Feb. 14, 2014	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2015	Sep. 30, 2014
Cash Dividends
Dividends declared (in dollars per share)									$ 0.51				$ 0.42				$ 1.53	$ 1.26
Quarter One
Dividends Payable
Date declared											Feb. 19, 2015				Feb. 20, 2014
Date paid											May 15, 2015				May 15, 2014
Cash Dividends
Dividends paid (in dollars per share)		$ 0.51				$ 0.42
Percentage increase in dividends declared											4.00%
Quarter Two
Dividends Payable
Date declared										Jun. 18, 2015				Jun. 19, 2014
Date paid										Aug. 14, 2015				Aug. 15, 2014
Cash Dividends
Dividends paid (in dollars per share)	$ 0.51				$ 0.42
Quarter Three
Dividends Payable
Date declared									Sep. 11, 2015				Sep. 19, 2014
Date of record									Oct. 15, 2015
Date paid									Nov. 16, 2015				Nov. 17, 2014
Cash Dividends
Dividends declared (in dollars per share)									$ 0.51				$ 0.42
Dividends paid (in dollars per share)				$ 0.42
Quarter Four
Dividends Payable
Date declared								Oct. 30, 2015				Oct. 20, 2014				Dec. 12, 2013
Date of record								Jan. 15, 2016
Date paid								Feb. 16, 2016				Feb. 13, 2015				Feb. 14, 2014
Cash Dividends
Dividends declared (in dollars per share)								$ 0.57				$ 0.49
Dividends paid (in dollars per share)			$ 0.49				$ 0.40
Percentage increase in dividends declared								12.00%				17.00%