Assumptions Used in Determining Benefit Obligation and Net Periodic Benefit Cost for Pension Plans (Detail)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan [Abstract]
Benefit obligations, Discount rate	0.53%	0.76%	0.82%
Benefit obligations, Rate of compensation increase	2.91%	3.08%	3.05%
Net periodic benefit cost, Discount rate	1.29%	1.66%	1.45%
Net periodic benefit cost, Rate of compensation increase	3.51%	3.18%	3.00%
Net periodic benefit cost, Expected return on plan assets	1.51%	1.89%	1.80%