Premises, Furniture, and Equipment - Rental Expense (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Abstract]
Lease expense charged to operations		$ 24,880	$ 18,666	$ 11,207
Accretion of operating lease intangible	[1]	(972)	(1,180)	(1,171)
Accretion of deferred gain on sale-leaseback transaction	[1]	(9,126)	(5,872)	(1,473)
Rental income from premises leased to others	[1]	(510)	(682)	(527)
Net operating lease expense		$ 14,272	$ 10,932	$ 8,036

[1] Included as reductions to net occupancy and equipment expense in the Consolidated Statements of Income.