Loans Loans, analysis of purchased credit impaired loans (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Allowance	$ 70,043	$ 68,172	$ 69,569	$ 72,454
Loans and Leases Receivable, Net Amount	6,143,380	5,746,855
Real estate: One-to-four family residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Allowance	599	916	2,281	1,252
Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Allowance	3,534	3,531	$ 3,180	$ 2,547
Purchased Credit Impaired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	157,251	197,350
Valuation discount resulting from acquisition accounting	11,591	16,444
Loans and Leases Receivable, Allowance	10,515	13,726
Loans and Leases Receivable, Net Amount	135,145	167,180
Purchased Credit Impaired Loans [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	21,606	38,784
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	20,643	27,195
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	94,795	106,308
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	115,438	133,503
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	832	2,326
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	1,726	1,834
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	2,558	4,160
Purchased Credit Impaired Loans [Member] | Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	$ 17,649	$ 20,903