Reconciliation of income tax computed at US Federal tax rates (Detail)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax [Abstract]
Statutory Income Tax	21.00%	35.00%	35.00%
Foreign Rate Differential, Inclusive of Foreign Rate Changes	(0.30%)	(1.10%)	(2.20%)
U.S. Deferred Tax Liability Remeasurement	0.00%	(7.00%)	0.00%
Deemed Repatriation Tax on Foreign Earnings and Profit (E&P)	1.80%	4.70%	0.00%
Tax Exempt Income	(1.30%)	(0.80%)	(0.80%)
Tax Credits	(2.40%)	(1.50%)	(1.60%)
Policyholder Reserves	(2.40%)	0.00%	0.00%
Other Items, Net	0.20%	(0.10%)	0.50%
Effective Tax	16.60%	29.20%	30.90%