Schedule of Share-based Compensation Expense (Parenthetical) (Detail) - USD ($)	3 Months Ended			12 Months Ended
	Dec. 31, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Special charges	$ 3,634,000	$ 1,750,000	$ 5,061,000	$ 10,445,000	$ 0	$ 16,339,000
Restricted shares expense acceleration
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Special charges						200,000
Share based awards, value of shares forfeited				0		1,200,000
Option expense acceleration
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Special charges						100,000
Options, value of shares forfeited				$ 0		$ 200,000