Loans Loans, analysis of purchased credit impaired loans (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Allowance	$ 68,172	$ 69,569	$ 72,454	$ 82,300
Loans and Leases Receivable, Net Amount	5,746,855	5,375,809
Real estate: One-to-four family residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Allowance	916	2,281	1,252	694
Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Allowance	3,531	3,180	$ 2,547	$ 2,437
Purchased Credit Impaired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	197,350	256,468
Valuation discount resulting from acquisition accounting	16,444	25,884
Loans and Leases Receivable, Allowance	13,726	16,336
Loans and Leases Receivable, Net Amount	167,180	214,248
Purchased Credit Impaired Loans [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	38,784	50,334
Purchased Credit Impaired Loans [Member] | Real estate: One-to-four family residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	27,195	31,981
Purchased Credit Impaired Loans [Member] | Commercial and Multifamily Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	106,308	140,398
Purchased Credit Impaired Loans [Member] | Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	133,503	172,379
Purchased Credit Impaired Loans [Member] | One-to-Four Family Residential Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	2,326	4,353
Purchased Credit Impaired Loans [Member] | Commercial and Multifamily Residential Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	1,834	2,588
Purchased Credit Impaired Loans [Member] | Real Estate Construction Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	4,160	6,941
Purchased Credit Impaired Loans [Member] | Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	$ 20,903	$ 26,814