Employee Benefit Plans (Narrative) (Detail) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended			9 Months Ended		12 Months Ended
	Mar. 31, 2017	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Defined benefit pension plans and defined benefit postretirement plans disclosure [Abstract]
Cash contributions for pension settlement							$ 84,800
Defined benefit plan, settlements benefit obligation		$ 152,388	$ 66,300	$ 0	$ 152,388	$ 0
Defined benefit plan, settlements plan assets			$ 127,200
Contribution for pension obligation	$ 34,000