Comprehensive income (Details) (USD $) In Thousands	6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010
Available for sale ("AFS") investment securities with other-than-temporary impairment ("OTTI"):
Unrealized holding gains, net, before-tax amount	$ (11,227)	$ (50,566)
Unrealized holding gains, net, income taxes	4,501	19,603
Unrealized holding gains, net, net of tax amount	(6,726)	(30,963)
Less: reclassification adjustment for gains realized in net income, before tax	3,814
Less: reclassification adjustment for gains realized in net income, income taxes	(1,497)
Less: reclassification adjustment for gains realized in net income, net	2,317
Less: OTTI charges recognized in net income AFS	(32,071)	(49,182)
Less: OTTI charges recognized in net income, income taxes	12,587	19,017
Less: OTTI charges recognized in net income, net	(19,484)	(30,165)
Net change for AFS investment securities with OTTI, before tax	17,030	(1,384)
Net change for AFS investment securities with OTTI, after tax	10,441	(798)
Net change for AFS investment securities with OTTI, income taxes	(6,589)	586
AFS investment securities - all other:
Unrealized holding gains, net, before-tax amount	77,869	221,196
Unrealized holding gains, net, income taxes	(30,368)	(86,386)
Unrealized holding gains, net, net of tax amount	47,501	134,810
Less: reclassification adjustment for gains/losses realized in net income, before-tax amount	146,115	(135)
Less: reclassification adjustment for gains/losses realized in net income, income taxes	(57,257)	39
Less: reclassification adjustment for gains/losses realized in net income, net	88,858	(96)
Net change for AFS investment securities - all other, before tax	(68,246)	221,331
Net change for AFS investment securities - all other, tax	26,889	(86,425)
Net change for AFS investment securities - all other, after tax	(41,357)	134,906
Unrealized holding gains on HTM securities, net, before-tax amount	(8,500)
Unrealized holding gains on HTM securities, net, income taxes	3,336
Unrealized holding gains on HTM securities, net, net of tax amount	(5,164)
Reclassification to income of unrealized holding losses before tax	(12)
Less: reclassification to income of unrealized holding losses tax	5
Less: reclassification to income of unrealized holding losses after tax	(7)
Less: OTTI charges recognized in net income, tax	4,121
Less: OTTI charges recognized in net income, before tax	(10,500)
Less: OTTI charges recognized in net income, after tax	(6,379)
Net change for investment securities with OTTI, before tax	2,012
Net change for investment securities with OTTI, tax	(790)
Net change for investment securities with OTTI, after tax	1,222
Reclassification to income of unrealized holding losses on securities previously transferred from AFS to HTM	2,967	4,374
Reclassification to income of unrealized holding losses on securities previously transferred from AFS to HTM, net of tax	1,802	2,658
Reclassification to income of unrealized holding losses on securities previously transferred from AFS to HTM, tax	(1,165)	(1,716)
Net unrealized losses on investment securities	(46,237)	224,321
Net unrealized gains/losses on investment securities, income taxes	18,345	(87,555)
Unrealized gains on investment securities	(27,892)	136,766
Reclassification to income for amortization of losses on terminated cash flow hedges to income, before-tax amount	(224)	(224)
Reclassification to income for amortization of losses on terminated cash flow hedges to income, income taxes	83	83
Reclassification to income for amortization of losses on terminated cash flow hedges to income, net	(141)	(141)
Foreign currency translation adjustment, before tax	313
Foreign currency translation adjustment, income taxes	(117)
Foreign currency translation adjustment	196
Defined benefit plans liability adjustment, before-tax amount	7,058	3,580
Defined benefit plans liability adjustment, income taxes	(2,770)	(1,405)
Defined benefit plans liability adjustment, net	4,288	2,175
Total Comprehensive Income, before-tax amount	(39,090)	227,677
Total Comprehensive Income, income taxes	15,541	(88,877)
Total Comprehensive Income, net	$ (23,549)	$ 138,800