Business Segments (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2017 USD ($) Segment	Mar. 31, 2016 USD ($)	Jun. 30, 2016 Segment	Dec. 31, 2016 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments (segment) | Segment	2		1
Interest income	$ 83,094	$ 73,398
Interest expense	20,670	15,767
Net interest income	62,424	57,631
Provision for loan losses	3,050	1,980
Non-interest income	5,427	5,267
Non-interest expense	30,147	31,871
Income from continuing operations before income tax expense	34,654	29,047
Income tax expense	7,730	9,739
Net income	25,747	18,184
Preferred stock dividends	3,615	1,286
Net income available to common shareholders	22,132	16,898
Goodwill and other intangibles	3,636			$ 3,639
Assets	9,906,636			9,382,736
Deposits	6,627,061			$ 6,846,980
Consolidated
Segment Reporting Information [Line Items]
Interest income	83,094	73,398
Interest expense	20,676	15,771
Net interest income	62,418	57,627
Provision for loan losses	3,050	1,980
Non-interest income	22,754	5,494
Non-interest expense	49,366	33,906
Income from continuing operations before income tax expense	32,756	27,235
Income tax expense	7,009	9,051
Net income	25,747	18,184
Preferred stock dividends	3,615	1,286
Net income available to common shareholders	22,132	16,898
Goodwill and other intangibles	17,618	3,648
Assets	9,906,636	9,038,873
Deposits	$ 7,335,480	6,478,615
Operating Segments | Community Business Banking
Segment Reporting Information [Line Items]
Effective tax rate	38.00%
Interest income	$ 78,832	71,673
Interest expense	20,656	15,764
Net interest income	58,176	55,909
Provision for loan losses	3,050	1,980
Non-interest income	5,427	5,267
Non-interest expense	30,147	31,871
Income from continuing operations before income tax expense	30,406	27,325
Income tax expense	6,116	9,085
Net income	24,290	18,240
Preferred stock dividends	3,615	1,286
Net income available to common shareholders	20,675	16,954
Goodwill and other intangibles	3,636	3,648
Assets	9,833,721	9,036,212
Deposits	6,627,061	6,141,880
Operating Segments | BankMobile
Segment Reporting Information [Line Items]
Interest income	4,262	1,725
Interest expense	20	7
Net interest income	4,242	1,718
Provision for loan losses	0	0
Non-interest income	17,327	227
Non-interest expense	19,219	2,035
Income from continuing operations before income tax expense	2,350	(90)
Income tax expense	893	(34)
Net income	1,457	(56)
Preferred stock dividends	0	0
Net income available to common shareholders	1,457	(56)
Goodwill and other intangibles	13,982	0
Assets	72,915	2,661
Deposits	708,419	336,735
Segment Reconciling Items
Segment Reporting Information [Line Items]
Interest income	$ 4,300	$ 1,700