Loans Loans, analysis of purchased credit impaired loans (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Allowance	$ 69,569	$ 72,454	$ 82,300	$ 57,985
Loans and Leases Receivable, Net Amount	5,375,809	4,444,842
One-to-Four Family Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Allowance	2,281	1,252	694	654
Consumer Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Allowance	3,180	2,547	2,437	2,719
Purchased Credit Impaired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	256,468	341,142
Valuation discount resulting from acquisition accounting	25,884	43,297
Loans and Leases Receivable, Allowance	16,336	20,174
Loans and Leases Receivable, Net Amount	214,248	277,671
Purchased Credit Impaired Loans [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	50,334	72,870
Purchased Credit Impaired Loans [Member] | One-to-Four Family Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	31,981	41,642
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	140,398	170,879
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	172,379	212,521
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	4,353	14,781
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	2,588	6,869
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	6,941	21,650
Purchased Credit Impaired Loans [Member] | Consumer Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	$ 26,814	$ 34,101