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Deposits - Composition of Deposits and Interest Expenses (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Schedule Of Deposits And Borrowings Maturities [Line Items] |  |  |
Balance | $ 5,427,891 | $ 5,272,377 | $ 4,876,611
Interest Expense | 25,330 | 19,692 | 12,944
Noninterest-bearing demand |  |  |
Schedule Of Deposits And Borrowings Maturities [Line Items] |  |  |
Balance | 1,387,712 | 1,263,833 | 1,227,766
Interest-bearing demand |  |  |
Schedule Of Deposits And Borrowings Maturities [Line Items] |  |  |
Balance | 603,141 | 638,300 | 616,188
Interest Expense | 67 | 111 | 818
Money market |  |  |
Schedule Of Deposits And Borrowings Maturities [Line Items] |  |  |
Balance | 1,146,156 | 936,461 | 605,184
Interest Expense | 9,204 | 4,199 | 1,299
Savings |  |  |
Schedule Of Deposits And Borrowings Maturities [Line Items] |  |  |
Balance | 893,119 | 1,050,131 | 1,061,265
Interest Expense | 2,081 | 2,002 | 1,712
Certificates of deposit |  |  |
Schedule Of Deposits And Borrowings Maturities [Line Items] |  |  |
Balance | 1,397,763 | 1,383,652 | 1,366,208
Interest Expense | $ 13,978 | $ 13,380 | $ 9,115

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- Definition Schedule Of Deposits And Borrowings Maturities [Line Items] + References No definition available. + Details
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- Definition The aggregate of all deposit liabilities held by the entity, including foreign and domestic, interest and noninterest bearing; may include demand deposits, saving deposits, Negotiable Order of Withdrawal (NOW) and time deposits among others. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.12) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 + Details
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- Definition Aggregate amount of interest expense on all deposits. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.6) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882 + Details
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