Disclosures About Fair Value of Financial Instruments - Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Financial assets:
Available-for-sale securities	$ 694,259	$ 274,619
Level 1
Financial assets:
Available-for-sale securities		112,881
Level 2
Financial assets:
Available-for-sale securities	694,259	161,738
Recurring [Member]
Financial assets:
Available-for-sale securities	694,259	274,619
Financial Liabilities:
Derivative liability		698
Recurring [Member] | Interest Rate Swaps
Financial assets:
Derivative asset		698
Recurring [Member] | Interest Rate Caps and Collars
Financial assets:
Derivative asset		1,307
Financial Liabilities:
Derivative liability		1,389
Recurring [Member] | Level 1
Financial assets:
Available-for-sale securities		112,881
Recurring [Member] | Level 2
Financial assets:
Available-for-sale securities	694,259	161,738
Recurring [Member] | Level 2 | Interest Rate Swaps
Financial assets:
Derivative asset		698
Recurring [Member] | Level 2 | Interest Rate Caps and Collars
Financial assets:
Derivative asset		1,307
Financial Liabilities:
Derivative liability		1,389
Commercial Customer | Recurring [Member] | Interest Rate Swaps
Financial assets:
Derivative asset	735
Financial Liabilities:
Derivative liability	728
Commercial Customer | Recurring [Member] | Interest Rate Caps and Collars
Financial assets:
Derivative asset	997
Financial Liabilities:
Derivative liability	43	5
Commercial Customer | Recurring [Member] | Level 2 | Interest Rate Swaps
Financial assets:
Derivative asset	735
Financial Liabilities:
Derivative liability	728	698
Commercial Customer | Recurring [Member] | Level 2 | Interest Rate Caps and Collars
Financial assets:
Derivative asset	997
Financial Liabilities:
Derivative liability	43	5
Correspondent | Recurring [Member] | Interest Rate Caps and Collars
Financial assets:
Derivative asset	44	5
Financial Liabilities:
Derivative liability	1,044
Correspondent | Recurring [Member] | Level 2 | Interest Rate Caps and Collars
Financial assets:
Derivative asset	44	$ 5
Financial Liabilities:
Derivative liability	$ 1,044