Carrying Amount and Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Carrying Amount
Financial Assets
Cash and cash equivalents	$ 203,790	$ 200,004
Debt securities, held-to-maturity	297,915	648,313
Loans receivable, net of ALLL	8,156,310	6,448,256
Total financial assets	8,658,015	7,296,573
Financial Liabilities
Term deposits	1,070,208	977,302
FHLB advances	440,175	353,995
Repurchase agreements and other borrowed funds	410,859	370,797
Subordinated debentures	134,051	126,135
Total financial liabilities	2,055,293	1,828,229
Estimated Fair Value | Level 1
Financial Assets
Cash and cash equivalents	203,790	200,004
Debt securities, held-to-maturity	0	0
Loans receivable, net of ALLL	0	0
Total financial assets	203,790	200,004
Financial Liabilities
Term deposits	0	0
FHLB advances	0	0
Repurchase agreements and other borrowed funds	0	0
Subordinated debentures	0	0
Total financial liabilities	0	0
Estimated Fair Value | Level 2
Financial Assets
Cash and cash equivalents	0	0
Debt securities, held-to-maturity	288,256	660,086
Loans receivable, net of ALLL	0	6,219,515
Total financial assets	288,256	6,879,601
Financial Liabilities
Term deposits	1,069,777	978,803
FHLB advances	439,615	352,886
Repurchase agreements and other borrowed funds	410,859	370,797
Subordinated debentures	120,302	98,023
Total financial liabilities	2,040,553	1,800,509
Estimated Fair Value | Level 3
Financial Assets
Cash and cash equivalents	0	0
Debt securities, held-to-maturity	0	0
Loans receivable, net of ALLL	8,079,112	114,771
Total financial assets	8,079,112	114,771
Financial Liabilities
Term deposits	0	0
FHLB advances	0	0
Repurchase agreements and other borrowed funds	0	0
Subordinated debentures	0	0
Total financial liabilities	$ 0	$ 0