Acquisitions - Assets Acquired and Liabilities Assumed - (Details) - USD ($) $ in Thousands			12 Months Ended
	Jun. 30, 2019	Jul. 01, 2018	Jun. 30, 2019	Sep. 30, 2019	Dec. 31, 2018
LIABILITIES ASSUMED
Goodwill recognized				$ 808,322	$ 808,726
Grandpoint Capital, Inc.
ASSETS ACQUIRED
Cash and cash equivalents	$ 147,551	$ 147,551	$ 147,551
Investment securities	392,858	395,905	392,858
Loans, gross	2,352,717	2,404,042	2,352,717
Allowance for loan losses	0	(18,665)	0
Fixed assets	9,122	6,015	9,122
Core deposit intangible	71,943	5,093	71,943
Deferred tax assets	5,028	14,185	5,028
Other assets	97,005	97,441	97,005
Total assets acquired	3,076,224	3,051,567	3,076,224
LIABILITIES ASSUMED
Deposits	2,506,929	2,506,663	2,506,929
Borrowings	254,923	255,155	254,923
Other Liabilities	24,859	23,687	24,859
Total liabilities assumed	2,786,711	2,785,505	2,786,711
Excess of assets acquired over liabilities assumed	289,513	266,062	289,513
Consideration paid	602,152	602,200
Goodwill recognized	$ 312,639	$ 312,600	312,639
Fair Value Adjustments
Cash and cash equivalents			0
Investment securities			(3,047)
Loans, gross			(51,325)
Allowance for loan losses			18,665
Fixed assets			3,107
Core deposit intangible			66,850
Deferred tax assets			(9,157)
Other assets			(436)
Total assets acquired			24,657
Deposits			266
Borrowings			(232)
Other Liabilities			1,172
Total liabilities assumed			1,206
Excess of assets acquired over liabilities assumed			$ 23,451