|
Segment Information - Concentration Risk (Details) (USD $)
In Millions, unless otherwise specified |
3 Months Ended | ||
|---|---|---|---|
|
Mar. 31, 2015
|
Mar. 31, 2014
|
Dec. 31, 2014
|
|
| Concentration Risk [Line Items] | |||
| Premiums, accounts and notes receivable, net | 3,309 | $ 2,757 | |
| Government Contracts Concentration Risk [Member] | CMS [Member] | |||
| Concentration Risk [Line Items] | |||
| Premiums, accounts and notes receivable, net | 1,100 | $ 800 | |
| Revenue Consolidated [Member] | Government Contracts Concentration Risk [Member] | CMS [Member] | |||
| Concentration Risk [Line Items] | |||
| Concentration percentage | 22.00% | 22.00% | |