earnings per share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share [Abstract]
Basic (per share)	$ 0.38	$ 0.03	$ (0.07)	$ 0.06	$ (0.16)	$ (0.07)	$ (0.57)	$ 0.16	$ 0.75	$ (0.55)	$ (0.52)
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent									$ 114,338	$ (184,904)	$ (178,341)
Net income from discontinued operations									99,472	24,976	27,345
Net income (loss)	$ 108,129	$ 9,259	$ (20,749)	$ 17,699	$ (44,508)	$ (20,720)	$ (167,141)	$ 47,465	$ 213,810	$ (159,928)	$ (150,996)
Basic (in shares)	285,754	285,942	285,866	287,796	287,052	292,663	294,103	291,367	286,347	291,318	289,348
Weighted Average Number Diluted Shares Outstanding Adjustment									3,778	0	0
Diluted (in shares)	291,598	288,648	285,866	292,359	287,052	292,663	294,103	295,995	290,125	291,318	289,348
Income (Loss) from Continuing Operations, Per Basic Share									$ 0.40	$ (0.63)	$ (0.62)
Discontinued Operation, Income (Loss) from Discontinued Operation, Net of Tax, Per Basic Share									0.35	0.08	0.10
Income (Loss) from Continuing Operations, Per Diluted Share									0.39	(0.63)	(0.62)
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share									0.35	0.08	0.10
Discontinued Operation, Income (Loss) from Discontinued Operation, Net of Tax, Per Diluted Share											0.10
Diluted (per share)	$ 0.37	$ 0.03	$ (0.07)	$ 0.06	$ (0.16)	$ (0.07)	$ (0.57)	$ 0.16	$ 0.74	$ (0.55)	$ (0.52)
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount									1,047	528	328
Weighted Average Number of Shares, Contingently Issuable									1,786	4,434	1,721