Loans and reserve for credit losses (Narrative) (Details) (USD $)	3 Months Ended			9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013	Sep. 30, 2014		Sep. 30, 2013	Dec. 31, 2013
Financing Receivable, Impaired [Line Items]
Percentage Of Real Estate Related Loans	72.00%			72.00%
Loans participated to third-parties	$ 31,400,000			$ 31,400,000			$ 11,300,000
Loans and Leases Receivable, Gross	1,466,710,000			1,466,710,000			996,232,000
Percentage of Acquired Loans Covered	14.70%			14.70%
Loans And Leases Receivable Gross, Percent	100.00%			100.00%
Loss Sharing Agreement, Expiration Period, Single Family Covered Assets				10 years
Loss Sharing Agreement, Covered Assets, Risk-Weighting Percent During Agreement Period				20.00%
Loss Sharing Agreement, Covered Assets, Potential Risk-Weighting Percent After Expiration				100.00%
Loss Sharing Agreement, Expiration Period, Non-Single Family Covered Assets				5 years
Loan loss provision	0		0	0		1,000,000
Loans and Leases Receivable, Allowance	21,351,000			21,351,000			20,857,000
Reductions in Loans Classified as Special Mention and Substandard				17,100,000
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	90,000			90,000			1,083,000
Impaired loans, Total recorded balance	33,488,000			33,488,000			40,467,000
Troubled Debt Restructuring
Financing Receivable, Impaired [Line Items]
Loans and Leases Receivable, Allowance	200,000			200,000			800,000
Impaired loans, Total recorded balance	26,900,000			26,900,000			33,200,000
Remaining Commitment To Lend Loan			0			0
Unallocated Financing Receivables
Financing Receivable, Impaired [Line Items]
Loan loss provision				2,300,000
Loans and Leases Receivable, Allowance	3,033,000			3,033,000			714,000
Originated Loans
Financing Receivable, Impaired [Line Items]
Percentage Of Real Estate Related Loans	66.50%			66.50%
Loans and Leases Receivable, Gross	1,126,601,000	[1]		1,126,601,000	[1]		996,232,000	[1]
Loans And Leases Receivable Gross, Percent	100.00%	[1]		100.00%	[1]		100.00%	[1]
Loans and Leases Receivable, Allowance	21,351,000	[1]		21,351,000	[1]		20,857,000	[1]
Reductions in Loans Classified as Special Mention and Substandard				(16,400,000)
Acquired Covered Loans
Financing Receivable, Impaired [Line Items]
Loans and Leases Receivable, Gross	50,062,000	[2],[3]		50,062,000	[2],[3]
Loans And Leases Receivable Gross, Percent	100.00%	[2]		100.00%	[2]
Loans and Leases Receivable, Net Reported Amount, Covered	50,062,000	[2]		50,062,000	[2]
Loans and Leases Receivable, Allowance	0	[2]		0	[2]
Acquired and Acquired Covered Loans
Financing Receivable, Impaired [Line Items]
Assets, Fair Value Adjustment				6,000,000
Loans and Leases Receivable, Gross	340,100,000	[2]		340,100,000	[2]
Substandard
Financing Receivable, Impaired [Line Items]
Loans and Leases Receivable, Gross	48,484,000			48,484,000			41,194,000
Substandard | Originated Loans
Financing Receivable, Impaired [Line Items]
Loans and Leases Receivable, Gross	33,230,000	[1]		33,230,000	[1]
Substandard | Acquired Covered Loans
Financing Receivable, Impaired [Line Items]
Loans and Leases Receivable, Net Reported Amount, Covered	7,907,000	[2]		7,907,000	[2]
Loans And Leases Receivable, Covered	51.80%			51.80%
Substandard | Acquired and Acquired Covered Loans
Financing Receivable, Impaired [Line Items]
Loans and Leases Receivable, Gross	$ 15,300,000	[2]		$ 15,300,000	[2]
Loans And Leases Receivable Gross, Percent	4.50%			4.50%
Loan Receivables | Acquired and Acquired Covered Loans
Financing Receivable, Impaired [Line Items]
Life of the loans				10 years

[1] Originated loans are loans organically made through the Company's normal and customary origination process

[2] Acquired covered loans are loans in the Home portfolio that are covered under FDIC loss share agreements

[3] Acquired covered loans acquired in the acquisition of Home that are covered under FDIC loss share agreements