Share Based Compensation (Summary of Future Compensation Expense in Connection With Vesting of Existing Time Based Restricted Share Awards) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total		$ 8,307
Restricted Stock [Member] | Year One [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total		3,960
Restricted Stock [Member] | Year Two [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total		2,776
Restricted Stock [Member] | Year Three [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total		1,420
Restricted Stock [Member] | 2017 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total		$ 151
Subsequent Event [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Future compensation expense	$ 600