Common Stock (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands				3 Months Ended				6 Months Ended		12 Months Ended
	Jul. 25, 2019	May 31, 2019	Jan. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Class of Stock [Line Items]
Common stock, dividends declared, per share				$ 0.385	$ 0.360	$ 0.360	$ 0.335	$ 0.745	$ 0.695	$ 1.465	$ 1.365
Under the Merger Agreement Max dividends declared per share before June 1, 2020								0.385
Under the Merger Agreement Max dividends declared per share on or after June 1, 2020.								$ 0.41
Treasury Stock, Shares, Retired		1,400,000
Dividends, Common Stock, Cash				$ 15,694	$ 14,658	$ 14,642	$ 13,615	$ 30,400	$ 28,300	$ 59,600	$ 55,400
Subsequent Event
Class of Stock [Line Items]
Common stock, dividends declared, per share	$ 0.385
Maximum
Class of Stock [Line Items]
Proceeds from issuance of common stock, requested			$ 200,000