Schedule II - Condensed Financial Information of Registrant - Condensed Balance Sheet of Registrant (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2010
ASSETS
Cash and cash equivalents	$ 1,899.7	$ 1,470.7	$ 1,137.4	$ 256.9
Receivables, net	611.3	414.4
Prepaid expenses and other current assets	75.9	53.1
Properties, net	441.0	221.6
Deferred charges and other assets	281.6	172.6
Consolidated total assets	27,908.8	25,200.4
LIABILITIES AND EQUITY
Long-term debt	4,909.7	2,165.0
Equity conversion feature of preferred stock (Note 6 and Note 18)	330.8	232.0
Deferred tax liabilities (Note 23)	492.8	382.4
Other liabilities (Note 17)	718.0	600.6
Total liabilities	26,445.9	23,282.3
Stockholders’ equity:
Common stock, $0.01 par; 500,000.0 thousand shares authorized; 142,381.1 and 140,184.0 thousand shares issued and outstanding at September 30, 2013 and 2012, respectively.	1.4	1.4
Accumulated deficit	(192.4)	(98.2)
Accumulated other comprehensive income	87.7	413.2
Total permanent equity	1,133.5	1,598.9	1,373.0	1,177.9
Total liabilities and equity	27,908.8	25,200.4
HGI
ASSETS
Cash and cash equivalents	256.9	235.8	134.8	84.3
Short-term investments	0	34.0
Receivables, net	41.0
Prepaid expenses and other current assets	3.3	6.4
Total current assets	301.2	276.2
Investments in subsidiaries and affiliates	2,049.0	2,001.8
Advances to consolidated subsidiaries	9.5	9.4
Properties, net	0.5	0.3
Deferred charges and other assets	23.1	11.6
Consolidated total assets	2,383.3	2,299.3
LIABILITIES AND EQUITY
Accounts payable	1.4	0.8
Accrued and other current liabilities	69.6	61.7
Total current liabilities	71.0	62.5
Long-term debt	924.2	497.7
Equity conversion feature of preferred stock (Note 6 and Note 18)	330.8	232.0
Employee benefit obligations	3.0	5.1
Deferred tax liabilities (Note 23)	0	4.9
Other liabilities (Note 17)	0.3	0.3
Total liabilities	1,329.3	802.5
Temporary equity
Redeemable preferred stock	329.3	319.2
Stockholders’ equity:
Common stock, $0.01 par; 500,000.0 thousand shares authorized; 142,381.1 and 140,184.0 thousand shares issued and outstanding at September 30, 2013 and 2012, respectively.	1.4	1.4
Additional paid-in capital	828.0	861.2
Accumulated deficit	(192.4)	(98.2)
Accumulated other comprehensive income	87.7	413.2
Total permanent equity	724.7	1,177.6
Total liabilities and equity	$ 2,383.3	$ 2,299.3