Equity (Details 2) - $ / shares						3 Months Ended							6 Months Ended
	May. 15, 2015	Feb. 13, 2015	Aug. 15, 2014	May. 15, 2014	Feb. 14, 2014	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Jun. 30, 2015	Jun. 30, 2014
Cash Dividends
Dividends declared (in dollars per share)						$ 0.51				$ 0.42			$ 1.02	$ 0.84
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	$ 0.40
Percentage increase in dividends declared							4.00%
Quarter Two
Dividends Payable
Date declared						Jun. 18, 2015				Jun. 19, 2014
Date of record						Jul. 15, 2015
Date paid										Aug. 15, 2014
Cash Dividends
Dividends declared (in dollars per share)						$ 0.51
Dividends paid (in dollars per share)			$ 0.42
Quarter Three
Cash Dividends
Dividends declared (in dollars per share)									$ 0.42
Quarter Four
Dividends Payable
Date declared								Oct. 20, 2014				Dec. 12, 2013
Date paid								Feb. 13, 2015				Feb. 14, 2014
Cash Dividends
Dividends declared (in dollars per share)								$ 0.49
Dividends paid (in dollars per share)		$ 0.49			$ 0.40
Percentage increase in dividends declared								17.00%