Bank subsidiary (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Net income	$ 41,061	$ 39,273	$ 75,213	$ 78,062
Net unrealized gains (losses) on securities:
Net unrealized gains (losses) on securities arising during the period, net of (taxes) benefits, of $5,485 and ($721) for the three months ended June 30, 2013 and 2012 and $6,032 and ($572) for the six months ended June 30, 2013 and 2012, respectively	(8,307)	1,093	(9,135)	867
Net unrealized gains (losses) on securities arising during the period, (taxes) benefits	5,485	(721)	6,032	(572)
Less: reclassification adjustment for net realized gains included in net income, net of taxes of $488 and $53 for the three months ended June 30, 2013 and 2012 and $488 and $53 for the six months ended June 30, 2013 and 2012, respectively	(738)	(81)	(738)	(81)
Less: reclassification adjustment for net realized gains included in net income, taxes	488	53	488	53
Retirement benefit plans:
Less: amortization of prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits of $308 and $168 for the three months ended June 30, 2013 and 2012 and $1,732 and $332 for the six months ended June 30, 2013 and 2012, respectively	5,680	3,768	11,701	7,641
Less: amortization of net loss, prior service gain and transition obligation included in net periodic benefit cost, tax benefits	3,630	2,405	7,476	4,878
Other comprehensive income (loss), net of taxes	(8,305)	1,550	(8,366)	1,861
Comprehensive income	32,283	40,350	65,901	78,977
American Savings Bank (ASB)
Net income	15,919	14,189	30,074	30,066
Net unrealized gains (losses) on securities:
Net unrealized gains (losses) on securities arising during the period, net of (taxes) benefits, of $5,485 and ($721) for the three months ended June 30, 2013 and 2012 and $6,032 and ($572) for the six months ended June 30, 2013 and 2012, respectively	(8,307)	1,093	(9,135)	867
Net unrealized gains (losses) on securities arising during the period, (taxes) benefits	5,485	(721)	6,032	(572)
Less: reclassification adjustment for net realized gains included in net income, net of taxes of $488 and $53 for the three months ended June 30, 2013 and 2012 and $488 and $53 for the six months ended June 30, 2013 and 2012, respectively	(738)	(81)	(738)	(81)
Less: reclassification adjustment for net realized gains included in net income, taxes	488	53	488	53
Retirement benefit plans:
Less: amortization of prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits of $308 and $168 for the three months ended June 30, 2013 and 2012 and $1,732 and $332 for the six months ended June 30, 2013 and 2012, respectively	466	255	2,623	503
Less: amortization of net loss, prior service gain and transition obligation included in net periodic benefit cost, tax benefits	308	168	1,732	332
Other comprehensive income (loss), net of taxes	(8,579)	1,267	(7,250)	1,289
Comprehensive income	$ 7,340	$ 15,456	$ 22,824	$ 31,355