Nature of Operations and Basis of Presentation - Other Income (Deductions) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Other Income and Expenses [Abstract]
Change in COLI policies	$ (3,900)	$ (300)	$ (2,600)	$ 2,900	$ (200)	$ 7,200
Interest income	624	772	1,375	1,881	2,096	1,920
Foreign transaction gain (loss)	(302)	0	(874)	0	(1,052)	0
Miscellaneous income and (expense)	(82)	(32)	873	134	122	(94)
Total other income (deductions)	$ (3,660)	$ 440	$ (1,226)	$ 4,915	$ 966	$ 9,026