Business Segments (Details) $ in Thousands	3 Months Ended		6 Months Ended	9 Months Ended
	Sep. 30, 2016 USD ($) Segment	Sep. 30, 2015 USD ($)	Jun. 30, 2016 Segment	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments (segment) | Segment	2		1
Interest income	$ 84,212	$ 63,736		$ 238,931	$ 182,137
Interest expense	19,627	13,802		53,561	39,315
Net interest income	64,585	49,934		185,370	142,822
Provision for loan losses	88	2,094		2,854	14,393
Non-interest income	27,486	6,171		41,237	18,297
Non-interest expense	56,218	30,307		128,306	83,432
Income before income tax expense	35,765	23,704		95,447	63,294
Income tax expense	14,576	8,415		37,129	22,497
Net income	21,189	15,289		58,318	40,797
Preferred stock dividends	2,552	980		5,900	1,487
Net income available to common shareholders	18,637	14,309		52,418	39,310
Goodwill and other intangibles	16,924	3,654		16,924	3,654	$ 3,651
Total assets	9,602,610	7,596,176		9,602,610	7,596,176	8,398,205
Total deposits	$ 7,388,970	5,785,194		7,388,970	5,785,194	$ 5,909,501
Operating Segments | Community Business Banking
Segment Reporting Information [Line Items]
Effective tax rate	38.00%
Interest income	$ 82,828	62,153		234,513	177,215
Interest expense	19,620	13,795		53,539	39,299
Net interest income	63,208	48,358		180,974	137,916
Provision for loan losses	(162)	2,094		2,605	14,393
Non-interest income	11,121	6,160		22,241	18,272
Non-interest expense	36,864	28,467		101,053	78,344
Income before income tax expense	37,627	23,957		99,557	63,451
Income tax expense	15,284	8,511		38,691	22,557
Net income	22,343	15,446		60,866	40,894
Preferred stock dividends	2,552	980		5,900	1,487
Net income available to common shareholders	19,791	14,466		54,966	39,407
Goodwill and other intangibles	3,642	3,654		3,642	3,654
Total assets	9,532,281	7,593,556		9,532,281	7,593,556
Total deposits	6,855,788	5,423,717		6,855,788	5,423,717
Operating Segments | BankMobile
Segment Reporting Information [Line Items]
Interest income	1,384	1,583		4,418	4,922
Interest expense	7	7		22	16
Net interest income	1,377	1,576		4,396	4,906
Provision for loan losses	250	0		249	0
Non-interest income	16,365	11		18,996	25
Non-interest expense	19,354	1,840		27,253	5,088
Income before income tax expense	(1,862)	(253)		(4,110)	(157)
Income tax expense	(708)	(96)		(1,562)	(60)
Net income	(1,154)	(157)		(2,548)	(97)
Preferred stock dividends	0	0		0	0
Net income available to common shareholders	(1,154)	(157)		(2,548)	(97)
Goodwill and other intangibles	13,282	0		13,282	0
Total assets	70,329	2,620		70,329	2,620
Total deposits	533,182	361,477		533,182	361,477
Segment Reconciling Items
Segment Reporting Information [Line Items]
Interest income	$ 1,400	$ 1,600		$ 4,400	$ 4,900