Stockholders' Equity Dividends (Details) - $ / shares	3 Months Ended		9 Months Ended
	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2017	Jan. 31, 2016
Class of Stock [Line Items]
Common Stock, Dividends, Per Share, Declared	$ 0.365	$ 0.34	$ 0.705	$ 0.655
July 2016 dividend payment [Member]
Class of Stock [Line Items]
Dividends Payable, Date Declared, Month and Year			May 26, 2016
Dividends Payable, Date of Record			Jun. 06, 2016
Dividends Payable, Date to be Paid			Jul. 01, 2016
Common Stock, Dividends, Per Share, Declared			$ 0.17
October 2016 dividend payment [Member]
Class of Stock [Line Items]
Dividends Payable, Date Declared, Month and Year			Jul. 28, 2016
Dividends Payable, Date of Record			Sep. 01, 2016
Dividends Payable, Date to be Paid			Oct. 03, 2016
Common Stock, Dividends, Per Share, Declared			$ 0.17
January 2017 dividend payment [Member]
Class of Stock [Line Items]
Dividends Payable, Date Declared, Month and Year			Nov. 17, 2016
Dividends Payable, Date of Record			Dec. 02, 2016
Dividends Payable, Date to be Paid			Jan. 03, 2017
Common Stock, Dividends, Per Share, Declared			$ 0.1825
April 2017 dividend payment [Member]
Class of Stock [Line Items]
Dividends Payable, Date Declared, Month and Year			Jan. 24, 2017
Dividends Payable, Date of Record			Mar. 06, 2017
Dividends Payable, Date to be Paid			Apr. 03, 2017
Common Stock, Dividends, Per Share, Declared			$ 0.1825