Earnings Per Share - Summary of Basic and Diluted EPS (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended		12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Sep. 30, 2016
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Document Fiscal Year Focus	2017
Discontinued Operation, Income (Loss) from Discontinued Operation, Net of Tax, Per Diluted Share	$ 1.19	$ (0.06)
Weighted Average Number of Shares Outstanding, Diluted	199,185	197,507
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent		$ (2.5)
Net income (loss) attributable to common and participating preferred stockholders	$ 212.2	(33.9)
Net Income (Loss) Attributable to Parent	212.2	(33.9)
Income (Loss) from Continuing Operations Attributable to Parent	$ (25.5)	$ (21.8)
Participating shares at end of period:
Weighted-average common shares outstanding - basic	199,185	197,507
Net income (loss) per common share attributable to controlling interest:
Basic (in dollars per share)	$ 1.06	$ (0.17)
Income (Loss) from Continuing Operations, Per Diluted Share	(0.13)	(0.11)
Discontinued Operation, Income (Loss) from Discontinued Operation, Net of Tax, Per Basic Share	1.19	(0.06)
Earnings Per Share, Diluted	1.06	(0.17)
Income (Loss) from Continuing Operations, Per Basic Share	$ (0.13)	$ (0.11)
Stock option awards [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	1,567	1,303
Restricted stock awards [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	1,326	2,822
HGI [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Document Fiscal Year Focus	2016
HGI [Member] | Warrant [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price	$ 13.13		$ 13.13
Discontinued Operations, Held-for-sale [Member] | HGI [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net Income (Loss) Attributable to Parent	$ 237.7	$ (12.1)