Common Stock (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended						9 Months Ended		12 Months Ended
	Oct. 17, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Class of Stock [Line Items]
Common stock, dividends declared, per share		$ 0.385	$ 0.385	$ 0.360	$ 0.360	$ 0.360	$ 0.335	$ 1.130	$ 1.055	$ 1.49	$ 1.39
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
Dividends, Common Stock, Cash		$ 15,683	$ 15,694	$ 14,658	$ 14,641	$ 14,642	$ 13,615	$ 46,000	$ 42,900	$ 60,600	$ 56,500
Subsequent Event
Class of Stock [Line Items]
Common stock, dividends declared, per share	$ 0.385