Provisions for Federal and State Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current Income Tax Provision
Federal	$ 0	$ 0	$ 0
State			3,530
Total Current Income Taxes			3,530
Deferred Income Provision
Federal	13,675	11,209	12,413
State	3,862	4,145	(500)
Total Deferred Income Taxes	17,537	15,354	11,913
Total Income Tax Expense	$ 17,537	$ 15,354	$ 15,443