Employee and Agent Benefits - Target Plan Asset Allocation (Details)	12 Months Ended
	Dec. 31, 2015
Qualified defined benefit pension plans | U.S. equity portfolios | Minimum
Asset category target allocation
Asset category target allocation	0%
Qualified defined benefit pension plans | U.S. equity portfolios | Maximum
Asset category target allocation
Asset category target allocation	45%
Qualified defined benefit pension plans | International equity portfolios | Minimum
Asset category target allocation
Asset category target allocation	0%
Qualified defined benefit pension plans | International equity portfolios | Maximum
Asset category target allocation
Asset category target allocation	15%
Qualified defined benefit pension plans | Fixed income security portfolios | Minimum
Asset category target allocation
Asset category target allocation	30%
Qualified defined benefit pension plans | Fixed income security portfolios | Maximum
Asset category target allocation
Asset category target allocation	100%
Qualified defined benefit pension plans | Real estate investment portfolios | Minimum
Asset category target allocation
Asset category target allocation	0%
Qualified defined benefit pension plans | Real estate investment portfolios | Maximum
Asset category target allocation
Asset category target allocation	10%
Other postretirement benefits | U.S. equity portfolios
Asset category target allocation
Asset category target allocation	45%
Other postretirement benefits | International equity portfolios
Asset category target allocation
Asset category target allocation	30%
Other postretirement benefits | Fixed income security portfolios
Asset category target allocation
Asset category target allocation	25%