Goodwill and Intangible Assets (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, net		$ 125,271	$ 134,849
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
2020		20,297
2021		18,599
2022		16,320
2023		14,443
2024		12,663
Thereafter		42,949
Goodwill [Roll Forward]
Goodwill, Beginning Balance		1,049,263	447,430
Goodwill recognized during period	[1]		601,833
Adjustment	[1]	(1,172)
Goodwill, Ending Balance		1,048,091	1,049,263
Commercial [Member]
Goodwill [Roll Forward]
Goodwill, Beginning Balance		313,270	313,270
Goodwill recognized during period	[1]		0
Adjustment	[1]	600,661
Goodwill, Ending Balance		913,931	313,270
Consumer [Member]
Goodwill [Roll Forward]
Goodwill, Beginning Balance		43,458	43,458
Goodwill recognized during period	[1]		0
Adjustment	[1]	0
Goodwill, Ending Balance		43,458	43,458
Wealth Management [Member]
Goodwill [Roll Forward]
Goodwill, Beginning Balance		90,702	90,702
Goodwill recognized during period	[1]		0
Adjustment	[1]	0
Goodwill, Ending Balance		90,702	90,702
Funds Management and Other [Member]
Goodwill [Roll Forward]
Goodwill, Beginning Balance		601,833	0
Goodwill recognized during period	[1]		601,833
Adjustment	[1]	(601,833)
Goodwill, Ending Balance		0	601,833
Core deposits premiums [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross		103,200	103,200
Accumulated amortization		19,364	5,032
Finite-lived intangible assets, net		83,836	98,168
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
2020		12,892
2021		11,893
2022		10,981
2023		10,145
2024		9,379
Thereafter		28,546
Other identifiable intangible assets [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross		74,372	63,497
Accumulated amortization		32,937	26,816
Finite-lived intangible assets, net		41,435	$ 36,681
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
2020		7,405
2021		6,706
2022		5,339
2023		4,298
2024		3,284
Thereafter		$ 14,403

[1] Goodwill related to the CoBiz acquisition was not yet allocated to the operating segments as of December 31, 2018 and was included in Funds Management and Other in 2018 then allocated during 2019.