Goodwill and Intangible Assets (Schedule of Goodwill and Intangible Assets) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Goodwill and Intangible Assets [Line Items]
Indefinite-lived Intangible Assets (Excluding Goodwill)		$ 919	$ 919	$ 919
Intangible Assets, Net (Excluding Goodwill)		35,458	45,937	58,173
Goodwill and Intangible Assets [Roll Forward]
Total goodwill, beginning of period		765,842	765,842	382,762
Established through acquisitions	[1]	0	0	383,080
Total goodwill, end of period		765,842	765,842	765,842
Core deposit intangible, net, beginning of period		45,937
CDI current period amortization		(10,479)	(12,236)	(6,333)
Total core deposit intangible, end of period		35,458	45,937
Total goodwill and intangible assets, end of period		801,300	811,779	824,015
Core Deposits [Member]
Goodwill and Intangible Assets [Roll Forward]
Gross core deposit intangible balance, beginning of period		105,473	105,473	58,598
Accumulated amortization, beginning of period		(60,455)	(48,219)	(41,886)
Core deposit intangible, net, beginning of period		45,018	57,254	16,712
Established through acquisitions	[1]	0	0	46,875
CDI current period amortization		(10,479)	(12,236)	(6,333)
Total core deposit intangible, end of period		$ 34,539	$ 45,018	$ 57,254
Estimated life of CDI, in years		10 years

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