Valuation and Qualifying Accounts - Summary of Valuation and Qualifying Accounts (Detail) - Allowance for Uncollectible Accounts [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance, beginning of period	$ 3,868	$ 3,737	$ 3,881
Additions - Charged to costs and expenses	1,463	1,942	2,227
Deductions	(1,880)	(1,811)	(2,371)
Balance, end of period	$ 3,451	$ 3,868	$ 3,737