Income Taxes - Component of Income Taxes Expenses (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Components of income tax expense (benefit):
Currently payable (receivable)	$ 100	$ 800
Deferred income taxes (benefit)	(28,700)	4,200	$ (41,900)
Income tax expense (benefit)	$ (28,611)	$ 5,003	$ (41,911)