Equity (Details 2) - $ / shares												3 Months Ended									12 Months Ended
	Nov. 16, 2015	Aug. 14, 2015	May. 15, 2015	Feb. 13, 2015	Feb. 13, 2015	Nov. 17, 2014	Nov. 17, 2014	Aug. 15, 2014	May. 15, 2014	Feb. 14, 2014	Jan. 04, 2013	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	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	[1]
Cash Dividends
Dividends declared (in dollars per share)											$ 0.40	$ 0.57	$ 0.51	$ 0.51	$ 0.51	$ 0.49	$ 0.42	$ 0.42	$ 0.42		$ 2.10	$ 1.75	$ 2.00
Dividend Paid 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%
Dividend Paid 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
Dividend Paid Quarter Three
Dividends Payable
Date declared													Sep. 11, 2015				Sep. 19, 2014
Date paid													Nov. 16, 2015				Nov. 17, 2014
Cash Dividends
Dividends declared (in dollars per share)													$ 0.51
Dividends paid (in dollars per share)	$ 0.51					$ 0.42	$ 0.42
Dividend Paid 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
Dividends paid (in dollars per share)				$ 0.49	$ 0.49					$ 0.40
Percentage increase in dividends declared												12.00%				17.00%

[1] On January 4, 2013, a cash dividend of $0.40 per share of common stock was declared from pre-separation earnings and was recorded as a reduction of additional paid-in capital.