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Comprehensive Income (Details) - USD ($) $ / shares in Units, $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2019 | Sep. 30, 2018 | Sep. 30, 2019 | Sep. 30, 2018
Comprehensive Income Detail [Abstract] |  |  |  |
Comprehensive income available for common stockholders | $ 30 | $ 38 | $ 114 | $ 113
Earnings per share on comprehensive income: |  |  |  |
Basic | $ 0.39 | $ 0.51 | $ 1.50 | $ 1.55
Diluted | $ 0.39 | $ 0.50 | $ 1.49 | $ 1.54
Weighted average common shares outstanding: |  |  |  |
Weighted Average Number of Shares Outstanding, Basic | 76,742,789 | 74,649,469 | 75,910,080 | 72,879,007
Weighted Average Number of Shares Outstanding, Diluted | 77,348,976 | 75,360,089 | 76,646,487 | 73,745,640

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- Definition Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=114867106&loc=d3e557-108580 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 1B -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=114867106&loc=SL7669625-108580 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 1A -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=114867106&loc=SL7669619-108580 + Details
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