Income Taxes - Additional Information (Details) - USD ($)		1 Months Ended		11 Months Ended	12 Months Ended
	Sep. 30, 2017	Nov. 30, 2015	Mar. 31, 2013	Aug. 31, 2016	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Operating Loss Carryforwards [Line Items]
Value of warrants			$ 242,400,000	$ 1,565,900,000
Term of warrants			10 years
Tax benefit adjustment, increase in fair value of warrants		$ 456,000,000		$ 52,000,000
Valuation allowance - increase (decrease)					$ 45,500,000	$ 33,400,000
Excess tax benefit from the exercise of stock options					36,700,000
Excess tax benefits related to share-based compensation						0	$ 88,116,000
Income tax payments, net of refunds					105,000,000	17,500,000	299,600,000
Unrecognized tax benefits, including interest and penalties	$ 338,400,000				338,400,000	88,200,000
Unrecognized tax benefits, including interest and penalties, net of federal benefit	304,200,000				304,200,000	63,100,000
Unrecognized tax benefits that would impact effective tax rate	289,200,000				289,200,000	48,000,000
Unrecognized tax benefits, interest and penalties	14,500,000				14,500,000	12,400,000
Litigation settlement, unrecognized tax benefit	323,869,000				323,869,000	$ 75,766,000	$ 44,722,000	$ 42,908,000
Reduction of unrecognized tax benefits reasonably possible	5,200,000				5,200,000
Undistributed earnings of international subsidiaries	1,300,000,000				1,300,000,000
Capital loss carryforward [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	$ 64,300,000				64,300,000
Minimum [Member] | Capital loss carryforward [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards, term	1 year
Minimum [Member] | Research and development tax credit carryforward [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards, term	18 years
Maximum [Member] | Capital loss carryforward [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards, term	3 years
Maximum [Member] | Research and development tax credit carryforward [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards, term	20 years
Federal [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	$ 26,500,000				26,500,000
Federal [Member] | Alternative minimum tax credit carryforwards [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	140,000,000				140,000,000
Federal [Member] | Research and development tax credit carryforward [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	$ 9,900,000				9,900,000
Federal [Member] | Minimum [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards, term	1 year
Federal [Member] | Maximum [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards, term	19 years
State [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	$ 118,100,000				118,100,000
Tax credit carryforwards	$ 2,600,000				2,600,000
State [Member] | Minimum [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards, term	1 year
State [Member] | Maximum [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards, term	20 years
Foreign [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	$ 23,800,000				23,800,000
Tax credit carryforwards	12,300,000				12,300,000
Foreign [Member] | Alternative minimum tax credit carryforwards [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	$ 2,100,000				2,100,000
Foreign [Member] | Minimum [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards, term	1 year
Foreign [Member] | Maximum [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards, term	9 years
Share based compensation expense [Member]
Operating Loss Carryforwards [Line Items]
Valuation allowance - increase (decrease)					17,100,000
USAO-EDNY Matter [Member]
Operating Loss Carryforwards [Line Items]
Litigation settlement, unrecognized tax benefit	$ 235,100,000				235,100,000
Litigation settlement reserve	$ 625,000,000				$ 625,000,000