Variable Interest Entities (Details) $ in Billions	9 Months Ended
	Sep. 30, 2016 USD ($) LimitedPartnerships
Variable Interest Entity [Line Items]
Methodology for determining whether the Company is primary beneficiary	When the Company becomes involved with a variable interest entity, as well as when there is a change in the Company’s involvement with an entity, the Company evaluates the following to determine if it is the primary beneficiary and must consolidate the entity: the structure and purpose of the entity; the risks and rewards created by and shared through the entity; and the Company’s ability to direct its activities, receive its benefits and absorb its losses relative to the other parties involved with the entity including its sponsors, equity holders, guarantors, creditors and servicers.
Investment Entities [Member]
Variable Interest Entity [Line Items]
Maximum exposure to loss related to arrangements with variable interest entity	$ 0.6
Non-controlling interest percentage
Security And Real Estate Limited Partnerships [Member]
Variable Interest Entity [Line Items]
Maximum exposure to loss related to arrangements with variable interest entity	$ 1.9
Number of limited partnerships defined as variable interest entities | LimitedPartnerships	100
Commitments to contribute additional cash, amount	$ 0.9
Security And Real Estate Limited Partnerships [Member] | Maximum [Member]
Variable Interest Entity [Line Items]
Non-controlling interest percentage	10.00%
Security And Real Estate Limited Partnerships [Member] | Other Long Term Investments [Member]
Variable Interest Entity [Line Items]
Carrying amount of assets	$ 1.0
Independent Physician Associations [Member]
Variable Interest Entity [Line Items]
Maximum exposure to loss related to arrangements with variable interest entity