Lease Exit and Related Charges (Changes to Accrued Loss on Excess Office Facilities) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Mar. 31, 2018
Disclosure Changes To Accrued Loss On Excess Office Facilities [Abstract]
Percent reduction in office space				15.00%
Accrued Loss on Excess Office Facilities [Roll Forward]
Accrued loss, beginning of year	$ 2,058	$ 3,186	$ 2,595
Additions and adjustments to the lease loss accrual, including estimated sublease income	(454)	0	2,428
Less amounts paid, net of sublease income	(382)	(1,128)	(1,837)
Accrued loss, end of year	1,222	2,058	3,186
Less current portion (included in Accrued and other current liabilities)	(346)	(341)	(1,024)
Accrued loss, non-current portion (included in Other long term liabilities)	$ 876	$ 1,717	$ 2,162