Employer Sponsored Benefit Plans (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Components of net periodic benefit cost
Interest cost	$ 517	$ 665	$ 1,033	$ 1,331
Expected return on assets	(590)	(793)	(1,180)	(1,587)
Amortization of actuarial loss	224	180	449	360
Net periodic benefit cost	$ 151	$ 52	$ 302	$ 104