Stock Compensation - Summary of Stock Options Outstanding and Related Activity (Detail) - HGI [Member] - $ / shares shares in Thousands	3 Months Ended		12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Sep. 30, 2016
Warrant [Member]
Options (in shares):
Stock options outstanding at September 30, 2016	1,200
Stock options outstanding at December 31, 2016	1,200		1,200
Weighted Average Exercise Price (in dollars per share):
Granted	$ 13.13		$ 13.13
Weighted Average Grant Date Fair Value (in dollars per share):
Granted	$ 3.22		$ 3.22
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number	1,200
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Exercise Price	$ 13.13	$ 13.125
Restricted award expected to vest	$ 3.22
Employee Stock Option [Member]
Options (in shares):
Stock options outstanding at September 30, 2016	4,231
Granted	318	28
Exercised	(77)
Stock options outstanding at December 31, 2016	4,472		4,231
Stock options vested and exercisable at December 31, 2016	3,902
Weighted Average Exercise Price (in dollars per share):
Granted	$ 15.39
Exercised	12.33
Stock options outstanding at December 31, 2016	9.85		$ 9.48
Stock options vested and exercisable at December 31, 2016	9.20
Weighted Average Grant Date Fair Value (in dollars per share):
Granted	5.96
Exercised	4.52
Stock options outstanding at December 31, 2016	3.94		$ 3.80
Stock options vested and exercisable at December 31, 2016	$ 3.71
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number	4,472
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Exercise Price	$ 9.85
Restricted award expected to vest	$ 3.94