Employee Benefit Plans - Components of Net Periodic Benefit Income for the Pension Plans (Detail) - Pension Benefits [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2,293	$ 1,910	$ 7,083	$ 5,746
Interest cost	24,503	25,760	73,746	76,792
Expected return on plan assets	(37,487)	(36,208)	(112,809)	(108,639)
Amortization of prior service credit	(141)	(468)	(423)	(1,400)
Amortization of actuarial loss	9,528	6,745	28,769	19,953
Net periodic benefit income	$ (1,304)	$ (2,261)	$ (3,634)	$ (7,548)