Income Taxes - Change in Deferred Tax Asset Valuation Allowances (Detail) - Valuation Allowance of Deferred Tax Assets - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Taxes [Line Items]
Balance at the beginning of the year	$ (87,623)	$ (16,599)	$ (14,781)
Charged to provision for income taxes:
Other state valuation allowances	500	(1,050)	0
Other federal valuation allowances	(477)	(511)	363
Rabbi trust valuation allowance	(1,066)	3,494	3,619
Other	(34)	0	0
Balance at the end of the year	(107,174)	(87,623)	(16,599)
State
Charged to provision for income taxes:
Net operating loss carryforwards	(17,374)	(30,457)	(5,800)
Federal
Charged to provision for income taxes:
Net operating loss carryforwards	$ (1,100)	$ (42,500)	$ 0