Lease Exit and Related Charges (Changes to Accrued Loss on Excess Office Facilities) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	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
Additions and adjustments to the lease loss accrual, including estimated sublease income	(454)
Less amounts paid, net of sublease income	(382)
Accrued loss, end of year	1,222
Less current portion (included in Accrued and other current liabilities)	(346)
Accrued loss, non-current portion (included in Other long term liabilities)	$ 876