Bank subsidiary (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Net income	$ 34,152	$ 38,789
Net unrealized losses on securities:
Net unrealized losses on securities arising during the period, net of tax benefits, of $547and $149 for the three months ended March 31, 2013 and 2012, respectively	(828)	(226)
Net unrealized losses on securities arising during the period, tax benefits	547	149
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 $1,424 and $164 for the three months ended March 31, 2013 and 2012, respectively	6,021	3,873
Less: amortization of net loss, prior service gain and transition obligation included in net periodic benefit cost, tax benefits	3,846	2,473
Other comprehensive income (loss), net of taxes	(61)	311
Comprehensive income	33,618	38,627
American Savings Bank (ASB)
Net income	14,155	15,877
Net unrealized losses on securities:
Net unrealized losses on securities arising during the period, net of tax benefits, of $547and $149 for the three months ended March 31, 2013 and 2012, respectively	(828)	(226)
Net unrealized losses on securities arising during the period, tax benefits	547	149
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 $1,424 and $164 for the three months ended March 31, 2013 and 2012, respectively	2,157	248
Less: amortization of net loss, prior service gain and transition obligation included in net periodic benefit cost, tax benefits	1,424	164
Other comprehensive income (loss), net of taxes	1,329	22
Comprehensive income	$ 15,484	$ 15,899