Bank subsidiary (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Net income for common stock	$ 38,316	$ 28,462
Net unrealized losses on securities:
Net unrealized losses on securities arising during the period, net of tax benefits, of $149 and $414 for the three months ended March 31, 2012 and 2011, respectively	(226)	(626)
Retirement benefit plans:
Less: amortization of net loss, prior service gain and transition obligation included in net periodic benefit cost, net of tax benefits of $2,212 and $1,448 for the three months ended March 31, 2012 and 2011, respectively	3,873	1,039
Other comprehensive income (loss), net of taxes	311	(1,838)
Comprehensive net income	38,627	26,624
Net unrealized losses on securities arising during the period, taxes (tax benefits)	149	414
Amortization of net loss, prior service gain and transition obligation included in net periodic benefit cost, taxes (tax benefits)	(2,473)	(631)
American Savings Bank (ASB)
Net income for common stock	15,877	13,851
Net unrealized losses on securities:
Net unrealized losses on securities arising during the period, net of tax benefits, of $149 and $414 for the three months ended March 31, 2012 and 2011, respectively	(226)	(626)
Retirement benefit plans:
Less: amortization of net loss, prior service gain and transition obligation included in net periodic benefit cost, net of tax benefits of $2,212 and $1,448 for the three months ended March 31, 2012 and 2011, respectively	248	(1,639)
Other comprehensive income (loss), net of taxes	22	(2,265)
Comprehensive net income	15,899	11,586
Net unrealized losses on securities arising during the period, taxes (tax benefits)	149	414
Amortization of net loss, prior service gain and transition obligation included in net periodic benefit cost, taxes (tax benefits)	$ (164)	$ 1,082