Benefit Plans - Qualified and Non-Qualified Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income or Loss (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Compensation and Retirement Disclosure [Abstract]
Net loss (gain)	$ 27,902	$ (37,955)
Prior service cost	0	119
Recognized prior service cost	0	(2,386)
Amortization of actuarial loss	(226)	(1,970)	(2,401)
Total recognized in other comprehensive income	27,676	(42,192)
Total recognized in net periodic pension expense and other comprehensive income (before tax)	$ 21,833	$ (36,840)