Employee Benefit Plans - Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income (Loss) (Detail) - Pension Benefits [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Current year actuarial loss (gain)	$ 44,930	$ 312,011	$ (368,587)
Recognition of actuarial loss	(38,197)	(26,791)	(83,934)
Recognition of prior service credit	565	638	7,538
Total recognized in other comprehensive income (loss)	7,298	285,858	(444,983)
Total recognized in net periodic benefit (income) cost and other comprehensive income (loss)	$ 1,450	$ 276,303	$ (393,912)