Employee Benefit Plans - Components of Net Periodic Benefit Income for the Pension Plans (Detail) - Pension Benefits [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2,124	$ 2,403	$ 4,151	$ 4,790
Interest cost	26,219	24,631	52,310	49,243
Expected return on plan assets	(39,333)	(37,675)	(78,471)	(75,322)
Amortization of prior service credit	(108)	(141)	(216)	(282)
Amortization of actuarial loss	7,875	9,628	15,670	19,241
Net periodic benefit income	$ (3,223)	$ (1,154)	$ (6,556)	$ (2,330)