Components of Net Periodic Benefit Cost (Narrative) (Detail) - USD ($)	9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2006	Dec. 31, 2002
Compensation and Retirement Disclosure [Abstract]
Defined benefit plan age of attainment	21 years
Service period for employees of coverage age, years	1 year
Defined benefit plan, percentage vested	100.00%
Benefits paid		$ 4,300,000
Charge associated with employees that elected to receive lump sum pension distributions		$ 1,300,000
Retiree benefits eliminated if less than service period, years			10 years	10 years
Defined benefit plan, contributions by employer	$ 0