Bank subsidiary (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Net income	$ 39,273	$ 27,612	$ 78,062	$ 56,547
Net unrealized losses on securities:
Net unrealized gains on securities arising during the period, net of taxes of $721 and $2,755 for the three months ended June 30, 2012 and 2011 and $572 and $2,341 for the six months ended June 30, 2012 and 2011, respectively	1,093	4,061	867	3,435
Net unrealized gains on securities arising during the period, taxes	721	2,755	572	2,341
Less: reclassification adjustment for net realized gains included in net income, net of taxes of $53 and $2 for the three months ended June 30, 2012 and 2011 and $53 and $2 for the six months ended June 30, 2012 and 2011, respectively	(81)	(3)	(81)	(3)
Less: reclassification adjustment to net realized gains, taxes	53	2	53	2
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 $2,405 and $1,477 for the three months ended June 30, 2012 and 2011 and $4,878 and $2,108 for the six months ended June 30, 2012 and 2011, respectively	3,768	2,449	7,641	3,488
Less: amortization of net loss, prior service gain and transition obligation included in net periodic benefit cost, tax benefits	2,405	1,477	4,878	2,108
Other comprehensive income, net of taxes	1,550	4,467	1,861	2,629
Comprehensive income	40,350	31,606	78,977	58,230
American Savings Bank (ASB)
Net income	14,189	15,195	30,066	29,046
Net unrealized losses on securities:
Net unrealized gains on securities arising during the period, net of taxes of $721 and $2,755 for the three months ended June 30, 2012 and 2011 and $572 and $2,341 for the six months ended June 30, 2012 and 2011, respectively	1,093	4,061	867	3,435
Net unrealized gains on securities arising during the period, taxes	721	2,755	572	2,341
Less: reclassification adjustment for net realized gains included in net income, net of taxes of $53 and $2 for the three months ended June 30, 2012 and 2011 and $53 and $2 for the six months ended June 30, 2012 and 2011, respectively	(81)	(3)	(81)	(3)
Less: reclassification adjustment to net realized gains, taxes	53	2	53	2
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 $2,405 and $1,477 for the three months ended June 30, 2012 and 2011 and $4,878 and $2,108 for the six months ended June 30, 2012 and 2011, respectively	255	186	503	(1,453)
Less: amortization of net loss, prior service gain and transition obligation included in net periodic benefit cost, tax benefits	(168)	(5)	(332)	1,077
Other comprehensive income, net of taxes	1,267	4,244	1,289	1,979
Comprehensive income	$ 15,456	$ 19,439	$ 31,355	$ 31,025