Bank subsidiary (Details 3) (USD $)	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012	Dec. 31, 2011
Assets
Available-for-sale investment and mortgage-related securities	$ 659,400,000	$ 671,358,000
Investment in stock of Federal Home Loan Bank of Seattle	95,152,000	96,022,000
Loans receivable held for investment, net	3,803,002,000	3,737,233,000
Loans held for sale, at lower of cost or fair value	5,351,000	26,005,000
Other	527,820,000	494,414,000
Goodwill	82,190,000	82,190,000
Total assets	10,298,569,000	10,149,132,000
Liabilities and shareholder's equity
Other	471,217,000	526,613,000
Total liabilities	8,657,011,000	8,520,974,000
Common stock	1,413,700,000	1,403,484,000
Retained earnings	220,049,000	216,804,000		198,397,000
Accumulated other comprehensive income (loss), net of taxes:
Net unrealized gains on securities	9,933,000	10,761,000
Retirement benefit plans	(35,716,000)	(36,424,000)
Accumulated other comprehensive income (loss), net of taxes	(26,484,000)	(26,423,000)
Total shareholders' equity	1,607,265,000	1,593,865,000	1,550,855,000	1,528,706,000
Total liabilities and shareholders' equity	10,298,569,000	10,149,132,000
Other assets
Premises and equipment, net	3,640,308,000	3,594,829,000
Total other assets	527,820,000	494,414,000
Other liabilities
Total other liabilities	471,217,000	526,613,000
Balance Sheet related disclosures
Securities sold under agreements to repurchase	143,000,000	146,000,000
American Savings Bank (ASB)
Assets
Cash and cash equivalents	224,870,000	184,430,000
Available-for-sale investment and mortgage-related securities	659,400,000	671,358,000
Investment in stock of Federal Home Loan Bank of Seattle	95,152,000	96,022,000
Loans receivable held for investment	3,845,732,000	3,779,218,000
Allowance for loan losses	(42,730,000)	(41,985,000)
Loans receivable held for investment, net	3,803,002,000	3,737,233,000
Loans held for sale, at lower of cost or fair value	5,351,000	26,005,000
Other	246,420,000	244,435,000
Goodwill	82,190,000	82,190,000
Total assets	5,116,385,000	5,041,673,000
Liabilities and shareholder's equity
Deposit liabilities-noninterest-bearing	1,223,921,000	1,164,308,000
Deposit liabilities-interest-bearing	3,088,699,000	3,065,608,000
Other borrowings	193,233,000	195,926,000
Other	106,337,000	117,752,000
Total liabilities	4,612,190,000	4,543,594,000
Common stock	334,344,000	333,712,000
Retained earnings	183,918,000	179,763,000
Accumulated other comprehensive income (loss), net of taxes:
Net unrealized gains on securities	9,933,000	10,761,000
Retirement benefit plans	(24,000,000)	(26,157,000)
Accumulated other comprehensive income (loss), net of taxes	(14,067,000)	(15,396,000)
Total shareholders' equity	504,195,000	498,079,000
Total liabilities and shareholders' equity	5,116,385,000	5,041,673,000
Other assets
Bank-owned life insurance	126,798,000	125,726,000
Premises and equipment, net	64,217,000	62,458,000
Prepaid expenses	13,189,000	13,199,000
Accrued interest receivable	13,773,000	13,228,000
Mortgage-servicing rights	11,400,000	10,818,000
Real estate acquired in settlement of loans, net	3,785,000	6,050,000
Other	13,258,000	12,956,000
Total other assets	246,420,000	244,435,000
Other liabilities
Accrued expenses	13,723,000	17,103,000
Federal and state income taxes payable	42,205,000	35,408,000
Cashier's checks	21,810,000	23,478,000
Advance payments by borrowers	6,443,000	9,685,000
Other	22,156,000	32,078,000
Total other liabilities	106,337,000	117,752,000
Balance Sheet related disclosures
Securities sold under agreements to repurchase	143,000,000	146,000,000
Advances from Federal Home Loan Bank	$ 50,000,000	$ 50,000,000