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Fair Value Measurements (Details 3) - USD ($) $ in Millions | Jun. 30, 2018 | Dec. 31, 2017
--- | --- | ---
Debt securities |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Cost Basis | $ 783 | $ 774
Unrealized Gains | 2 | 11
Unrealized Losses | (27) | (17)
Fair Value | 758 | 768
Equity securities |  |
Amortized cost basis, unrealized gains and losses and fair values of investments in available-for-sale securities |  |
Cost Basis | 265 | 254
Unrealized Gains | 31 | 40
Unrealized Losses | (1) | 0
Fair Value | $ 295 | $ 294

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- Definition This item represents the cost of debt securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (aa) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.2) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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