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Investments (Narrative) (Details) | 12 Months Ended
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Dec. 31, 2015 USD ($) investments | Dec. 31, 2014 USD ($)
Investments [Abstract] |  |
Available-for-sale Securities, Aggregate fair value, continuous unrealized loss position, 12 months or more | $ 280,126,000 | $ 832,420,000
Number of investments in continuous unrealized loss position for more than twelve months | investments | 39 |
Unrealized losses related to marketability of securities or issuers ability to honor redemption obligations | $ 0 | 0
Investment value deemed to be OTTI | 0 |
Investment securities, aggregate carrying value, pledged as collateral | $ 4,730,000,000 | $ 4,370,000,000

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- Definition Unrealized Losses Related To Marketability Of Securities Or Issuers Ability To Honor Redemption Obligations + References No definition available. + Details
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- Definition This item represents the aggregate fair value of investments in debt and equity securities categorized neither as held-to-maturity nor trading securities that have been in a continuous unrealized loss position for twelve months or longer. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 6 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27290-111563 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27337-111563 + Details
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- Definition The amount by which the fair value of an investment is less than the amortized cost basis or carrying amount of that investment at the balance sheet date and the decline in fair value is deemed to be other than temporary, before considering whether or not such amount is recognized in earnings or other comprehensive income. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 35 -Paragraph 34 -URI http://asc.fasb.org/extlink&oid=27723805&loc=d3e25351-111560 + Details
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- Definition Sum of the carrying amounts as of the date of the latest financial statement presented of securities which are owned but transferred to another party to serve as collateral to partially or fully secure a debt obligation, repurchase agreement or other current or potential obligation, and for which the transferee is not permitted to sell or re-pledge them to an unrelated party. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 30 -Section 50 -Paragraph 1A -Subparagraph (b)(1)(i) -URI http://asc.fasb.org/extlink&oid=55761124&loc=SL6224234-111729 + Details
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