Subsequent Events - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified						3 Months Ended
	Mar. 31, 2014	Sep. 30, 2013	Mar. 31, 2014 Seven Point Seven Five Percent Senior Unsecured Notes [Member] HGI [Member]	Mar. 31, 2014 7.875% Senior Secured Notes, due July 15, 2019 [Member] HGI [Member]	Sep. 30, 2013 7.875% Senior Secured Notes, due July 15, 2019 [Member] HGI [Member]	Jun. 30, 2014 Common Stock Issued Per Share of Preferred Stock Held [Member] Series A Redeemable Convertible Preferred Stock [Member] Subsequent Event [Member]	Jun. 30, 2014 Common Stock Issued Per Share of Preferred Stock Held [Member] Series A-2 Redeemable Convertible Preferred Stock [Member] Subsequent Event [Member]
Subsequent Event [Line Items]
Conversion of Stock, Shares Issued						160.95	148.11
Long-term Debt	$ 5,405.2	$ 4,909.7	$ 200.0	$ 925.0	$ 925.0
Long-term debt, interest rate			7.75%	7.90%	0.00%