Subsequent Events (Details) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($) $ / shares
Subsequent Event [Line Items]
Common Stock, Dividends, Per Share, Cash Paid | $ / shares	$ 1.050	[1]
2018 ATM, Aggregate Value of Common Stock	$ 500
Common Stock [Member]
Subsequent Event [Line Items]
Dividends Payable, Date to be Paid	Mar. 30, 2018	[1]
Dividends Payable, Date of Record	Mar. 16, 2018	[1]
Dividends Payable, Date Declared	Feb. 21, 2018	[1]
Lightower Acquisition [Member]
Subsequent Event [Line Items]
Business Acquisition, Date of Acquisition Agreement	Nov. 01, 2017
2018 ATM Program [Member]
Subsequent Event [Line Items]
2018 ATM, Aggregate Value of Common Stock	$ 750

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