Equity (Details) - USD ($) $ / shares in Units, shares in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2017	Jun. 30, 2016
Dividends Payable [Line Items]
Common Stock, Dividends, Per Share, Cash Paid	[1]	$ 0.950	$ 0.950
Dividends, Common Stock, Cash	[1]	$ 350,300,000	$ 343,300,000
Common stock repurchased during period, shares				0.3
Purchases of capital stock				$ 22,594,000	$ 24,460,000
Common Stock [Member]
Dividends Payable [Line Items]
Dividends Payable, Date Declared	[1]	May 18, 2017	Feb. 17, 2017
Dividends Payable, Date to be Paid	[1]	Jun. 30, 2017	Mar. 31, 2017
Dividends Payable, Date of Record	[1]	Jun. 16, 2017	Mar. 17, 2017
At the Market Program [Member]
Dividends Payable [Line Items]
Payments of Stock Issuance Costs				$ 200,000

[1] Inclusive of dividends accrued for holders of unvested restricted stock units, which will be paid at the time the restricted stock units vest.