Accounting Policies - Unpaid Claims and Claims Expenses (Policies)	12 Months Ended
Dec. 31, 2016
Global Health Benefits Segment [Member]
Liability For Unpaid Claims And Claims Adjustment Expense [Line Items]
Liabilities for unpaid claims and claims expenses	Accounting policy. The Company uses actuarial principles and assumptions that are consistently applied each reporting period and recognizes the actuarial best estimate of the ultimate liability along with a margin for adverse deviation. This approach is consistent with actuarial standards of practice that the liabilities be adequate under moderately adverse conditions. This liability is primarily calculated using “completion factors” developed by comparing the claim incurral date to the date claims were paid. Completion factors are impacted by several key items including changes in: 1) electronic (auto-adjudication) versus manual claim processing, 2) provider claims submission rates, 3) membership and 4) the mix of products. The Company uses historical completion factors combined with an analysis of current trends and operational factors to develop current estimates of completion factors. The Company estimates the liability for claims incurred in each month by applying the current estimates of completion factors to the current paid claims data. This approach implicitly assumes that historical completion rates will be a useful indicator for the current period. For more recent months, the Company relies more heavily on medical cost trend analysis that reflects expected claim payment patterns and other relevant operational considerations. Medical cost trend is primarily impacted by medical service utilization and unit costs that are affected by changes in the level and mix of medical benefits offered, including inpatient, outpatient and pharmacy, the impact of copays and deductibles, changes in provider practices and changes in consumer demographics and consumption behavior. For each reporting period, the Company compares key assumptions used to establish the medical costs payable to actual experience. When actual experience differs from these assumptions, medical costs payable are adjusted through current period shareholders' net income. Additionally, the Company evaluates expected future developments and emerging trends that may impact key assumptions. The process used to determine this liability requires the Company to make critical accounting estimates that involve considerable judgment, reflecting the variability inherent in forecasting future claim payments. These estimates are highly sensitive to changes in the Company's key assumptions, specifically completion factors and medical cost trends.
Group Disability and Life, Global Supplemental Beneftits and Other Operations [Member]
Liability For Unpaid Claims And Claims Adjustment Expense [Line Items]
Liabilities for unpaid claims and claims expenses	Accounting policy. Liabilities for unpaid claims and claim expenses are established by book of business within the Company's Group Disability and Life, Global Supplemental Benefits and Other Operations segments. The Group Disability and Life segment's liability for unpaid claims and claim expenses consists of the following primary products: long-term and short-term disability, life insurance, and accident coverages. Unpaid claims and claim expenses consist of (1) case or claims reserves for known claims that are unpaid as of the balance sheet date; (2) incurred but not reported reserves for claims when the insured event has occurred but has not been reported to the Company; and (3) loss adjustment expense reserves for the expected costs of settling these claims. The Company consistently estimates incurred but not yet reported losses using actuarial principles and assumptions based on historical and projected claim incidence patterns, claim size and the expected payment period. The Company recognizes the actuarial best estimate of the ultimate liability within a level of confidence, consistent with actuarial standards of practice that the liabilities be adequate under moderately adverse conditions. When estimates of these liabilities change, the Company immediately records the adjustment in benefits and expenses. The Company's liability for disability claims reported but not yet paid is the present value of estimated future benefit payments over the expected disability period. The Company projects the expected disability period by using historical resolution rates combined with an analysis of current trends and operational factors to develop current estimates of resolution rates. Using the Company's experience, expected claim resolution rates may vary based upon the anticipated disability period, the covered benefit period, the cause of disability, the benefit design and the claimant's age, gender and income level. The gross monthly benefit is reduced (offset) by disability income received under other benefit programs, most commonly Social Security Disability Income, workers' compensation, statutory disability or other group benefit plans. For certain offsets not yet finalized, the Company estimates the probability and amount of future offset awards and lapses based on the Company's experience. The Company discounts certain liabilities, predominantly long-term disability, because benefits payments are made over extended periods. Discount rate assumptions for these liabilities are based on projected investment returns for the supporting asset portfolios.

Accounting Policies - Unpaid Claims and Claims Expenses (Policies)

12 Months Ended

Dec. 31, 2016

Liability For Unpaid Claims And Claims Adjustment Expense [Line Items]

Liabilities for unpaid claims and claims expenses

Accounting policy. The Company uses actuarial principles and assumptions that are consistently applied each reporting period and recognizes the actuarial best estimate of the ultimate liability along with a margin for adverse deviation. This approach is consistent with actuarial standards of practice that the liabilities be adequate under moderately adverse conditions.

This liability is primarily calculated using “completion factors” developed by comparing the claim incurral date to the date claims were paid. Completion factors are impacted by several key items including changes in: 1) electronic (auto-adjudication) versus manual claim processing, 2) provider claims submission rates, 3) membership and 4) the mix of products. The Company uses historical completion factors combined with an analysis of current trends and operational factors to develop current estimates of completion factors. The Company estimates the liability for claims incurred in each month by applying the current estimates of completion factors to the current paid claims data. This approach implicitly assumes that historical completion rates will be a useful indicator for the current period.

For more recent months, the Company relies more heavily on medical cost trend analysis that reflects expected claim payment patterns and other relevant operational considerations. Medical cost trend is primarily impacted by medical service utilization and unit costs that are affected by changes in the level and mix of medical benefits offered, including inpatient, outpatient and pharmacy, the impact of copays and deductibles, changes in provider practices and changes in consumer demographics and consumption behavior.

For each reporting period, the Company compares key assumptions used to establish the medical costs payable to actual experience. When actual experience differs from these assumptions, medical costs payable are adjusted through current period shareholders' net income. Additionally, the Company evaluates expected future developments and emerging trends that may impact key assumptions. The process used to determine this liability requires the Company to make critical accounting estimates that involve considerable judgment, reflecting the variability inherent in forecasting future claim payments. These estimates are highly sensitive to changes in the Company's key assumptions, specifically completion factors and medical cost trends.

Group Disability and Life, Global Supplemental Beneftits and Other Operations [Member]

Liability For Unpaid Claims And Claims Adjustment Expense [Line Items]

Liabilities for unpaid claims and claims expenses

Accounting policy. Liabilities for unpaid claims and claim expenses are established by book of business within the Company's Group Disability and Life, Global Supplemental Benefits and Other Operations segments. The Group Disability and Life segment's liability for unpaid claims and claim expenses consists of the following primary products: long-term and short-term disability, life insurance, and accident coverages. Unpaid claims and claim expenses consist of (1) case or claims reserves for known claims that are unpaid as of the balance sheet date; (2) incurred but not reported reserves for claims when the insured event has occurred but has not been reported to the Company; and (3) loss adjustment expense reserves for the expected costs of settling these claims. The Company consistently estimates incurred but not yet reported losses using actuarial principles and assumptions based on historical and projected claim incidence patterns, claim size and the expected payment period. The Company recognizes the actuarial best estimate of the ultimate liability within a level of confidence, consistent with actuarial standards of practice that the liabilities be adequate under moderately adverse conditions. When estimates of these liabilities change, the Company immediately records the adjustment in benefits and expenses.

The Company's liability for disability claims reported but not yet paid is the present value of estimated future benefit payments over the expected disability period. The Company projects the expected disability period by using historical resolution rates combined with an analysis of current trends and operational factors to develop current estimates of resolution rates. Using the Company's experience, expected claim resolution rates may vary based upon the anticipated disability period, the covered benefit period, the cause of disability, the benefit design and the claimant's age, gender and income level. The gross monthly benefit is reduced (offset) by disability income received under other benefit programs, most commonly Social Security Disability Income, workers' compensation, statutory disability or other group benefit plans. For certain offsets not yet finalized, the Company estimates the probability and amount of future offset awards and lapses based on the Company's experience.

The Company discounts certain liabilities, predominantly long-term disability, because benefits payments are made over extended periods. Discount rate assumptions for these liabilities are based on projected investment returns for the supporting asset portfolios.