Income Taxes (Schedule of Unrecognized Tax Benefits Roll Forward) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of period	$ 11,890	$ 12,629
Increase for prior year positions	447	275
Decrease for prior year positions	(3,316)
Lapse of statute of limitations	(434)	(1,014)
Balance at end of period	$ 8,587	$ 11,890