Goodwill and Intangible Assets (Schedule of Goodwill and Intangible Assets) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Goodwill and Intangible Assets [Line Items]
Indefinite-lived Intangible Assets (Excluding Goodwill)		$ 919	$ 919	$ 919
Intangible Assets, Net (Excluding Goodwill)		45,937	58,173	17,631
Goodwill and Intangible Assets [Roll Forward]
Total goodwill, beginning of period		765,842	382,762	382,762
Established through acquisitions	[1]	0	383,080	0
Total goodwill, end of period		765,842	765,842	382,762
Core deposit intangible, net, beginning of period		58,173
CDI current period amortization		(12,236)	(6,333)	(5,946)
Total core deposit intangible, end of period		45,937	58,173
Total goodwill and intangible assets, end of period		811,779	824,015	400,393
Core Deposits [Member]
Goodwill and Intangible Assets [Roll Forward]
Gross core deposit intangible balance, beginning of period		105,473	58,598	58,598
Accumulated amortization, beginning of period		(48,219)	(41,886)	(35,940)
Core deposit intangible, net, beginning of period		57,254	16,712	22,658
Established through acquisitions	[1]	0	46,875	0
CDI current period amortization		(12,236)	(6,333)	(5,946)
Total core deposit intangible, end of period		$ 45,018	$ 57,254	$ 16,712
Estimated life of CDI, in years		10 years

[1] See Note 2, “Business Combinations,” for additional information regarding the goodwill related to the acquisition of Pacific Continental on November 1, 2017.