Employee Benefit Plans (Combined Activity in Corporations Defined Benefit Pension Plans) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Compensation and Retirement Disclosure [Abstract]
Benefit obligation at beginning of year	$ 194,140	$ 199,637	$ 163,876
Interest cost	6,958	8,210	8,002
Actuarial (gain) loss	(8,298)	(6,489)	34,438
Benefits paid	(16,049)	(7,218)	(6,679)
Benefit obligation at end of year	176,751	194,140	199,637
Fair value of plan assets at beginning of year	163,270	168,185	164,769
Actual return on plan assets	5,174	1,567	9,428
Employer contributions	4,819	736	667
Benefits paid	(16,049)	(7,218)	(6,679)
Fair value of plan assets at end of year	157,214	163,270	168,185
Funded status of the plan at end of year and accrued (benefit) liability recognized	19,537	30,870	31,452
Accumulated benefit obligation at end of year	$ 176,751	$ 194,140	$ 199,637