Stockholders' Equity Dividends Declared (Details) - $ / shares	Aug. 02, 2017	May 04, 2017	Feb. 09, 2017	Nov. 01, 2016	Aug. 02, 2016	May 05, 2016	Feb. 10, 2016
Dividends Declared [Abstract]
Dividend, declaration date	Aug. 02, 2017	May 04, 2017	Feb. 09, 2017	Nov. 01, 2016	Aug. 02, 2016	May 05, 2016	Feb. 10, 2016
Dividend amount to be paid, per common share	$ 0.3850	$ 0.3750	$ 0.3650	$ 0.3550	$ 0.3450	$ 0.3350	$ 0.3250
Dividend, date of record	Aug. 14, 2017	May 19, 2017	Feb. 22, 2017	Nov. 18, 2016	Aug. 17, 2016	May 18, 2016	Feb. 23, 2016
Dividend, date to be paid	Sep. 01, 2017	Jun. 02, 2017	Mar. 09, 2017	Dec. 05, 2016	Sep. 01, 2016	Jun. 02, 2016	Mar. 10, 2016