Employee Benefit Plans - Changes in Plan Assets (Detail) - Pension Benefits [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Changes in plan assets
Fair value of plan assets at beginning of year	$ 1,912,736	$ 2,021,837
Actual return on plan assets	146,022	(45,529)
Foreign currency exchange rate changes	5,172	(33,382)
Employer contributions	53,663	54,543
Plan participants’ contributions	2,585	2,838
Benefits paid	(154,676)	(87,571)
Fair value of plan assets at end of year	$ 1,965,502	$ 1,912,736