FHLB and other borrowings (Details) - Schedule of components of FHLB and other borrowings and weighted average interest rates - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
By type of borrowing:
FHLB and other borrowings	$ 548,758	$ 495,553
Weighted average interest rates	1.33%	1.48%
By remaining period to maturity:
One year or less	$ 252,758	$ 258,553
One year or less	0.50%	0.50%
One to two years	$ 85,000	$ 30,000
One to two years	1.23%	1.40%
Two to three years	$ 56,000	$ 71,000
Two to three years	2.79%	2.33%
Three to four years	$ 90,000	$ 96,000
Three to four years	1.89%	2.67%
Four to five years	$ 25,000
Four to five years	1.85%
Greater than five years	$ 40,000	$ 40,000
Greater than five years	3.43%	3.42%
Federal Home Loan Bank Advances [Member]
By type of borrowing:
FHLB and other borrowings	$ 533,758	$ 464,553
Weighted average interest rates	1.20%	1.18%
Repurchase Agreements [Member]
By type of borrowing:
FHLB and other borrowings	$ 15,000	$ 31,000
Weighted average interest rates	5.95%	5.90%