Schedule II - Valuation and Qualifying Accounts (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reserve for Uncollectible Accounts:
Balance at Beginning of Period	$ 2,165	$ 2,302	$ 2,245
Additions	1,245	785	417
Deductions	(296)	(922)	(360)
Balance at End of Period	$ 3,114	$ 2,165	$ 2,302