Bank subsidiary (Details 3) (USD $)	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012	Dec. 31, 2011
Assets
Available-for-sale investment and mortgage-related securities	$ 560,172,000	$ 671,358,000
Investment in stock of Federal Home Loan Bank of Seattle	94,281,000	96,022,000
Loans receivable held for investment, net	3,912,630,000	3,737,233,000
Loans held for sale, at lower of cost or fair value	34,073,000	26,005,000
Other	454,898,000	494,414,000
Goodwill	82,190,000	82,190,000
Total assets	10,238,145,000	10,149,132,000
Liabilities and shareholder's equity
Other	496,375,000	526,613,000
Total liabilities	8,579,203,000	8,520,974,000
Common stock	1,429,371,000	1,403,484,000
Retained earnings	230,067,000	216,804,000
Accumulated other comprehensive income (loss), net of taxes:
Net unrealized gains on securities	888,000	10,761,000
Retirement benefit plans	(35,035,000)	(36,424,000)
Accumulated other comprehensive income (loss), net of taxes	(34,789,000)	(26,423,000)
Total shareholders' equity	1,624,649,000	1,593,865,000	1,575,776,000	1,528,706,000
Total liabilities and shareholders' equity	10,238,145,000	10,149,132,000
Other assets
Premises and equipment, net	3,701,905,000	3,594,829,000
Total other assets	454,898,000	494,414,000
Other liabilities
Total other liabilities	496,375,000	526,613,000
Balance Sheet related disclosures
Securities sold under agreements to repurchase	138,000,000	146,000,000
American Savings Bank (ASB)
Assets
Cash and cash equivalents	143,912,000	184,430,000
Available-for-sale investment and mortgage-related securities	560,172,000	671,358,000
Investment in stock of Federal Home Loan Bank of Seattle	94,281,000	96,022,000
Loans receivable held for investment	3,953,634,000	3,779,218,000
Allowance for loan losses	(41,004,000)	(41,985,000)
Loans receivable held for investment, net	3,912,630,000	3,737,233,000
Loans held for sale, at lower of cost or fair value	34,073,000	26,005,000
Other	241,513,000	244,435,000
Goodwill	82,190,000	82,190,000
Total assets	5,068,771,000	5,041,673,000
Liabilities and shareholder's equity
Deposit liabilities-noninterest-bearing	1,168,937,000	1,164,308,000
Deposit liabilities-interest-bearing	3,107,306,000	3,065,608,000
Other borrowings	187,884,000	195,926,000
Other	102,516,000	117,752,000
Total liabilities	4,566,643,000	4,543,594,000
Common stock	334,937,000	333,712,000
Retained earnings	189,837,000	179,763,000
Accumulated other comprehensive income (loss), net of taxes:
Net unrealized gains on securities	888,000	10,761,000
Retirement benefit plans	(23,534,000)	(26,157,000)
Accumulated other comprehensive income (loss), net of taxes	(22,646,000)	(15,396,000)
Total shareholders' equity	502,128,000	498,079,000
Total liabilities and shareholders' equity	5,068,771,000	5,041,673,000
Other assets
Bank-owned life insurance	127,851,000	125,726,000
Premises and equipment, net	68,124,000	62,458,000
Prepaid expenses	4,064,000	13,199,000
Accrued interest receivable	13,472,000	13,228,000
Mortgage-servicing rights	11,363,000	10,818,000
Real estate acquired in settlement of loans, net	2,987,000	6,050,000
Other	13,652,000	12,956,000
Total other assets	241,513,000	244,435,000
Other liabilities
Accrued expenses	15,456,000	17,103,000
Federal and state income taxes payable	30,932,000	35,408,000
Cashier's checks	22,737,000	23,478,000
Advance payments by borrowers	10,300,000	9,685,000
Other	23,091,000	32,078,000
Total other liabilities	102,516,000	117,752,000
Balance Sheet related disclosures
Securities sold under agreements to repurchase	138,000,000	146,000,000
Advances from Federal Home Loan Bank	$ 50,000,000	$ 50,000,000