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Goodwill and Intangible Assets (Schedule of Goodwill and Intangible Assets) (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended |  |  |  |
--- | --- | --- | --- | --- | --- | ---
Sep. 30, 2018 | Sep. 30, 2017 | Sep. 30, 2018 | Sep. 30, 2017 | Jun. 30, 2018 | Dec. 31, 2017 | Jun. 30, 2017 | Dec. 31, 2016
Goodwill and Intangible Assets [Roll Forward] |  |  |  |  |  |  |  |  |  |
Total goodwill, beginning of period |  |  |  | $ 765,842 |  |  |  |  |  |
Total goodwill, end of period | $ 765,842 | [1] | $ 382,762 | 765,842 | [1] | $ 382,762 |  |  |  |
CDI current period amortization | (3,070) |  | (1,188) | (9,346) |  | (3,786) |  |  |  |
Indefinite-lived Intangible Assets (Excluding Goodwill) | 919 |  | 919 | 919 |  | 919 |  |  |  |
Other intangible assets, net | 48,827 |  | 13,845 | 48,827 |  | 13,845 |  | $ 58,173 |  |
Total goodwill and intangible assets, end of period | 814,669 |  | 396,607 | $ 814,669 |  | 396,607 |  |  |  |
Core Deposits [Member] |  |  |  |  |  |  |  |  |  |
Goodwill and Intangible Assets [Line Items] |  |  |  |  |  |  |  |  |  |
Estimated life of CDI, in years |  |  |  | 10 years |  |  |  |  |  |
Goodwill and Intangible Assets [Roll Forward] |  |  |  |  |  |  |  |  |  |
Gross core deposit intangible balance, beginning of period |  |  |  |  |  |  | $ 105,473 | 105,473 | $ 58,598 | $ 58,598
Accumulated amortization at beginning of period |  |  |  |  |  |  | $ (54,495) | $ (48,219) | $ (44,484) | $ (41,886)
Core deposit intangible, net, beginning of period | 50,978 |  | 14,114 | $ 57,254 |  | 16,712 |  |  |  |
CDI current period amortization | (3,070) |  | (1,188) | (9,346) |  | (3,786) |  |  |  |
Total core deposit intangible, end of period | $ 47,908 |  | $ 12,926 | $ 47,908 |  | $ 12,926 |  |  |  |
[1] | See Note 3, “Business Combinations,” for additional information regarding goodwill and intangible assets recorded related to the acquisition of Pacific Continental on November 1, 2017.

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