Subsequent Events (Details) - $ / shares		3 Months Ended			9 Months Ended
		Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Sep. 30, 2017
Subsequent Event [Line Items]
Common Stock, Dividends, Per Share, Cash Paid	[1]	$ 0.950	$ 0.950	$ 0.950
Common Stock [Member]
Subsequent Event [Line Items]
Dividends Payable, Date to be Paid	[1]	Sep. 29, 2017	Jun. 30, 2017	Mar. 31, 2017
Dividends Payable, Date of Record	[1]	Sep. 15, 2017	Jun. 16, 2017	Mar. 17, 2017
Dividends Payable, Date Declared	[1]	Aug. 03, 2017	May 18, 2017	Feb. 17, 2017
Lightower Acquisition [Member]
Subsequent Event [Line Items]
Business Acquisition, Date of Acquisition Agreement					Nov. 01, 2017
Dividend Declared [Member] | Common Stock [Member]
Subsequent Event [Line Items]
Dividends Payable, Date to be Paid		Dec. 29, 2017
Dividends Payable, Date of Record		Dec. 15, 2017
Dividends Payable, Date Declared		Oct. 15, 2017
Paid subsequent to year end [Member]
Subsequent Event [Line Items]
Common Stock, Dividends, Per Share, Cash Paid		$ 1.050

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