Common Stock (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017
Dividends, Common Stock [Abstract]
Dividends, Common Stock, Cash	$ 13,615	$ 12,565	$ 54,300	$ 50,300