Stockholders' Equity (Narratives) (Details) - $ / shares	12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015
Dividends Declared
Dividends payable, date declared	Oct. 05, 2016
Dividend paid, amount per share	$ 1.00
Dividends payable, date of record	Oct. 20, 2016
Dividends payable, date to be paid	Nov. 03, 2016
Dividends declared one [Member]
Dividends Declared
Dividends payable, date declared	Mar. 15, 2016
Dividend paid, amount per share	$ 1.00
Dividends payable, date of record	Apr. 05, 2016
Dividends payable, date to be paid	Apr. 21, 2016
Dividends declared two [Member]
Dividends Declared
Dividends payable, date declared		Aug. 28, 2015
Dividend paid, amount per share		$ 3.00
Dividends payable, date of record		Sep. 16, 2015
Dividends payable, date to be paid		Oct. 02, 2015
Dividends declared three [Member]
Dividends Declared
Dividends payable, date declared		Jun. 04, 2015
Dividend paid, amount per share		$ 1.00
Dividends payable, date of record		Jun. 19, 2015
Dividends payable, date to be paid		Jul. 01, 2015
Dividends declared four [Member]
Dividends Declared
Dividends payable, date declared			Feb. 04, 2015
Dividend paid, amount per share			$ 1.00
Dividends payable, date of record			Mar. 06, 2015
Dividends payable, date to be paid			Mar. 17, 2015
Dividends declared five [Member]
Dividends Declared
Dividends payable, date declared	Feb. 08, 2017
Dividend paid, amount per share	$ 1.00
Dividends payable, date of record	Feb. 23, 2017
Dividends payable, date to be paid	Mar. 09, 2017