Parent Company Financial Information - STATEMENTS OF FINANCIAL CONDITION (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Percentage of capital stock of the Bank held	100.00%
Assets:
Other assets	$ 25,874	$ 22,958
Total Assets	4,036,311	2,789,599
Liabilities:
Subordinated debentures	69,383	69,263
Accrued expenses and other liabilities	33,732	30,108
Total liabilities	3,576,571	2,490,619
Total Stockholders’ Equity	459,740	298,980	$ 199,592	$ 175,226
Total Liabilities and Stockholders' Equity	4,036,311	2,789,599
Corporation
Assets:
Cash and cash equivalents	15,124	3,412
Investment in subsidiaries	513,606	359,143
Other assets	2,400	7,455
Total Assets	531,130	370,010
Liabilities:
Subordinated debentures	69,383	69,263
Accrued expenses and other liabilities	2,007	1,767
Total liabilities	71,390	71,030
Total Stockholders’ Equity	459,740	298,980
Total Liabilities and Stockholders' Equity	$ 531,130	$ 370,010