Income Taxes - Reconciliation of income taxes at the statutory rate to the provision for income taxes (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Earnings before income taxes (“EBT”)	$ 174	$ 223
Income taxes at statutory rate	37	78
Effect of stock-based compensation	(5)	(6)
Effect of tax exempt interest	(3)	(6)
Effect of dividends received deduction	(1)	(2)
Effect of foreign operations	3	6
Effect of nondeductible expenses	2	2
Effect of change in valuation allowance	0	(2)
Effect of other income tax reconciliation	0	(2)
Provision for income taxes as shown on the Statement of Earnings	$ 33	$ 68
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Income taxes at statutory rate as a percentage of EBT	21.00%	35.00%
Effect of stock-based compensation as a percentage of EBT	(3.00%)	(3.00%)
Effect of tax exempt interest as a percentage of EBT	(2.00%)	(3.00%)
Effect of dividends received deduction as a percentage of EBT	(0.00%)	(1.00%)
Effect of foreign operations as a percentage of EBT	2.00%	3.00%
Effect of nondeductible expenses as a percentage of EBT	1.00%	1.00%
Effect of change in valuation allowance as a percentage of EBT	0.00%	(1.00%)
Effect of other income tax reconciliation as a percentage of EBT	0.00%	(1.00%)
Provision for income taxes as shown on the Statement of Earnings as a percentage of EBT	19.00%	30.00%