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, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Current year actuarial loss	$ 152,415	$ 44,930	$ 312,011
Recognition of actuarial loss	(31,641)	(38,197)	(26,791)
Current year prior service cost	2,063	0	0
Recognition of prior service credit	432	565	638
Total recognized in other comprehensive income (loss)	123,269	7,298	285,858
Total recognized in net periodic benefit income and other comprehensive income (loss)	$ 109,877	$ 1,450	$ 276,303