Interim Financial Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2018
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 152,114	$ 184,972	$ 187,730	$ 160,981	$ 168,362	$ 195,105	$ 192,914	$ 164,464	$ 685,797	$ 720,845	$ 696,651
Operating expenses	(69,046)	(111,309)	(117,767)	(92,707)	(98,155)	(112,624)	(114,564)	(85,603)	(390,829)	(410,946)
Operating income	83,068	73,663	69,963	68,274	70,207	82,481	78,350	78,861	294,968	309,899	313,158
Net income	$ 55,920	$ 46,270	$ 39,964	$ 43,067	$ 41,179	$ 54,235	$ 43,838	$ 46,930	$ 185,221	$ 186,182	$ 288,862
Earnings Per Share, Basic	$ 0.98	$ 0.77	$ 0.66	$ 0.57	$ 0.55	$ 0.72	$ 0.58	$ 0.63	$ 2.93	$ 2.48	$ 3.83
Earnings Per Share, Diluted	$ 0.97	$ 0.77	$ 0.66	$ 0.57	$ 0.54	$ 0.72	$ 0.58	$ 0.62	$ 2.92	$ 2.46	$ 3.81