Comprehensive Income (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
Mar. 31, 2016	Mar. 31, 2015
Comprehensive Income Detail [Abstract]
Comprehensive income (loss) available for common stockholders	$ 39	$ (14)
Earnings per share on comprehensive income:
Basic	$ 0.61	$ (0.24)
Diluted	$ 0.60	$ (0.24)
Weighted average common shares outstanding:
Weighted Average Number of Shares Outstanding, Basic	63,985,477	58,473,348
Weighted Average Number of Shares Outstanding, Diluted	65,255,903	58,473,348

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.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Other Comprehensive Income
-URI http://asc.fasb.org/extlink&oid=51831270

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Comprehensive Income
-URI http://asc.fasb.org/extlink&oid=51831223

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=36458714&loc=d3e557-108580

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Net Income
-URI http://asc.fasb.org/extlink&oid=51831255

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Balance Type:	credit
Period Type:	duration