Retirement Benefit Plans - Assumed Health Care Cost Trend Rates (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($)
Schedule Of Sale Of Subsidiary [Abstract]
Aggregated service and interest cost, 1% Decrease in Rates	$ 886
Postretirement benefit obligation, 1% Decrease in Rates	19,820
Aggregated service and interest cost, Assumed Rates	1,008
Postretirement benefit obligation, Assumed Rates	22,281
Aggregated service and interest cost, 1% Increase in Rates	1,159
Postretirement benefit obligation, 1% Increase in Rates	$ 25,287