Allowance for loan losses (Details 5) (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011		Jun. 30, 2012	Dec. 31, 2011		Mar. 31, 2011	Dec. 31, 2010
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	$ 166,327		$ 129,979		$ 166,327		$ 129,979			$ 150,356
Accruing TDRs [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Current	92,430		117,343		92,430		117,343			100,358
Delinquent	54,573		5,263		54,573		5,263			38,245
Total	147,003		122,606		147,003		122,606			138,603
Nonaccruing TDRs [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Current	12,032		2,880		12,032		2,880			5,592
Delinquent	7,292		4,493		7,292		4,493			6,161
Total	19,324		7,373		19,324		7,373			11,753
Total Tdr Allowance [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance	15,365		6,881		15,365		6,881			12,114
Noncovered Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	23,753		12,607		23,753		12,607			15,002
Total Allowance	98,942		109,187		98,942		109,187		103,849	107,699		109,187	114,690
Financing Receivable, Allowance for Credit Losses, Charge-offs	(20,999)		(20,014)		(53,430)		(63,784)
Financing Receivable, Allowance for Credit Losses, Recoveries	6,127		5,410		17,813		16,521
Financing Receivable, Allowance for Credit Losses, Provisions	9,965		14,604		26,860		41,760
Noncovered Loans [Member] | Accruing TDRs [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Current	16,071		7,667		16,071		7,667			6,178
Delinquent	2,464		0		2,464		0			513
Total	18,535		7,667		18,535		7,667			6,691
Noncovered Loans [Member] | Nonaccruing TDRs [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Current	1,408		1,395		1,408		1,395			3,894
Delinquent	3,810		3,545		3,810		3,545			4,417
Total	5,218		4,940		5,218		4,940			8,311
Noncovered Loans [Member] | Total Tdr Allowance [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance	644		1,112		644		1,112			582
Noncovered Loans [Member] | Commercial and Industrial Financing Receivable [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	2,413		1,096		2,413		1,096			2,512
Noncovered Loans [Member] | Commercial and Industrial Financing Receivable [Member] | Accruing TDRs [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Current	955		129		955		129			91
Delinquent	0		0		0		0			0
Total	955		129		955		129			91
Noncovered Loans [Member] | Commercial and Industrial Financing Receivable [Member] | Nonaccruing TDRs [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Current	865		0		865		0			0
Delinquent	593		967		593		967			2,421
Total	1,458		967		1,458		967			2,421
Noncovered Loans [Member] | Commercial and Industrial Financing Receivable [Member] | Total Tdr Allowance [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance	126		215		126		215			247
Noncovered Loans [Member] | Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	17,763		8,068		17,763		8,068			9,167
Noncovered Loans [Member] | Commercial Real Estate [Member] | Accruing TDRs [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Current	11,609		4,778		11,609		4,778			3,305
Delinquent	2,464		0		2,464		0			513
Total	14,073		4,778		14,073		4,778			3,818
Noncovered Loans [Member] | Commercial Real Estate [Member] | Nonaccruing TDRs [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Current	473		1,215		473		1,215			3,590
Delinquent	3,217		2,075		3,217		2,075			1,759
Total	3,690		3,290		3,690		3,290			5,349
Noncovered Loans [Member] | Commercial Real Estate [Member] | Total Tdr Allowance [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance	401		125		401		125			236
Noncovered Loans [Member] | Commercial Real Estate Construction Financing Receivable [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	3,577		3,443		3,577		3,443			3,323
Noncovered Loans [Member] | Commercial Real Estate Construction Financing Receivable [Member] | Accruing TDRs [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Current	3,507		2,760		3,507		2,760			2,782
Delinquent	0		0		0		0			0
Total	3,507		2,760		3,507		2,760			2,782
Noncovered Loans [Member] | Commercial Real Estate Construction Financing Receivable [Member] | Nonaccruing TDRs [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Current	70		180		70		180			304
Delinquent	0		503		0		503			237
Total	70		683		70		683			541
Noncovered Loans [Member] | Commercial Real Estate Construction Financing Receivable [Member] | Total Tdr Allowance [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance	117		772		117		772			99
Noncovered Consumer Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	65,835		57,742		65,835		57,742			57,934
Noncovered Consumer Loans [Member] | Accruing TDRs [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Current	47,039		51,281		47,039		51,281			51,672
Delinquent	4,690		4,028		4,690		4,028			2,820
Total	51,729		55,309		51,729		55,309			54,492
Noncovered Consumer Loans [Member] | Nonaccruing TDRs [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Current	10,624		1,485		10,624		1,485			1,698
Delinquent	3,482		948		3,482		948			1,744
Total	14,106		2,433		14,106		2,433			3,442
Noncovered Consumer Loans [Member] | Total Tdr Allowance [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance	3,474		3,087		3,474		3,087			2,885
Noncovered Consumer Loans [Member] | Consumer Installment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	32,577		34,654		32,577		34,654			33,571
Noncovered Consumer Loans [Member] | Consumer Installment [Member] | Accruing TDRs [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Current	28,604		32,882		28,604		32,882			31,637
Delinquent	1,071		1,772		1,071		1,772			1,800
Total	29,675		34,654		29,675		34,654			33,437
Noncovered Consumer Loans [Member] | Consumer Installment [Member] | Nonaccruing TDRs [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Current	2,882		0		2,882		0			0
Delinquent	20		0		20		0			134
Total	2,902		0		2,902		0			134
Noncovered Consumer Loans [Member] | Consumer Installment [Member] | Total Tdr Allowance [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance	1,674		1,568		1,674		1,568			1,382
Noncovered Consumer Loans [Member] | Consumer Home Equity Lines Financing Receivable [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	6,922		4,413		6,922		4,413			4,763
Noncovered Consumer Loans [Member] | Consumer Home Equity Lines Financing Receivable [Member] | Accruing TDRs [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Current	5,394		3,885		5,394		3,885			4,226
Delinquent	171		528		171		528			222
Total	5,565		4,413		5,565		4,413			4,448
Noncovered Consumer Loans [Member] | Consumer Home Equity Lines Financing Receivable [Member] | Nonaccruing TDRs [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Current	1,131		0		1,131		0			76
Delinquent	226		0		226		0			239
Total	1,357		0		1,357		0			315
Noncovered Consumer Loans [Member] | Consumer Home Equity Lines Financing Receivable [Member] | Total Tdr Allowance [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance	95		52		95		52			31
Noncovered Consumer Loans [Member] | Consumer Credit Card Financing Receivable [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	1,767		2,359		1,767		2,359			2,202
Noncovered Consumer Loans [Member] | Consumer Credit Card Financing Receivable [Member] | Accruing TDRs [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Current	1,655		2,201		1,655		2,201			2,073
Delinquent	109		158		109		158			110
Total	1,764		2,359		1,764		2,359			2,183
Noncovered Consumer Loans [Member] | Consumer Credit Card Financing Receivable [Member] | Nonaccruing TDRs [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Current	0		0		0		0			0
Delinquent	3		0		3		0			19
Total	3		0		3		0			19
Noncovered Consumer Loans [Member] | Consumer Credit Card Financing Receivable [Member] | Total Tdr Allowance [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance	106		121		106		121			108
Noncovered Consumer Loans [Member] | Consumer Residential Mortgages Financing Receivable [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	24,569		16,316		24,569		16,316			17,398
Noncovered Consumer Loans [Member] | Consumer Residential Mortgages Financing Receivable [Member] | Accruing TDRs [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Current	11,386		12,313		11,386		12,313			13,736
Delinquent	3,339		1,570		3,339		1,570			688
Total	14,725		13,883		14,725		13,883			14,424
Noncovered Consumer Loans [Member] | Consumer Residential Mortgages Financing Receivable [Member] | Nonaccruing TDRs [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Current	6,611		1,485		6,611		1,485			1,622
Delinquent	3,233		948		3,233		948			1,352
Total	9,844		2,433		9,844		2,433			2,974
Noncovered Consumer Loans [Member] | Consumer Residential Mortgages Financing Receivable [Member] | Total Tdr Allowance [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance	1,599		1,346		1,599		1,346			1,364
Covered Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Current	732,470	[1]	1,061,263	[2]	732,470	[1]	1,061,263	[2]		954,689	[3]
Delinquent	310,588	[1]	365,484	[2]	310,588	[1]	365,484	[2]		336,787	[3]
Total	71,997		59,630		71,997		59,630			77,420
Covered Loans [Member] | Accruing TDRs [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Current	24,622		58,395		24,622		58,395			42,508
Delinquent	47,375		1,235		47,375		1,235			34,912
Total	71,997		59,630		71,997		59,630			77,420
Covered Loans [Member] | Nonaccruing TDRs [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Current	0		0		0		0			0
Delinquent	0		0		0		0			0
Total	0		0		0		0			0
Covered Loans [Member] | Total Tdr Allowance [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance	11,247		2,682		11,247		2,682			8,647
Covered Loans [Member] | Commercial and Industrial Financing Receivable [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	5,278		7,287		5,278		7,287			7,578
Covered Loans [Member] | Commercial and Industrial Financing Receivable [Member] | Accruing TDRs [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Current	1,000		6,052		1,000		6,052			1,587
Delinquent	4,278		1,235		4,278		1,235			5,991
Total	5,278		7,287		5,278		7,287			7,578
Covered Loans [Member] | Commercial and Industrial Financing Receivable [Member] | Nonaccruing TDRs [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Current	0		0		0		0			0
Delinquent	0		0		0		0			0
Total	0		0		0		0			0
Covered Loans [Member] | Commercial and Industrial Financing Receivable [Member] | Total Tdr Allowance [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance	1,527		746		1,527		746			1,384
Covered Loans [Member] | Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	52,080		41,403		52,080		41,403			57,786
Covered Loans [Member] | Commercial Real Estate [Member] | Accruing TDRs [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Current	17,298		41,403		17,298		41,403			35,083
Delinquent	34,782		0		34,782		0			22,703
Total	52,080		41,403		52,080		41,403			57,786
Covered Loans [Member] | Commercial Real Estate [Member] | Nonaccruing TDRs [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Current	0		0		0		0			0
Delinquent	0		0		0		0			0
Total	0		0		0		0			0
Covered Loans [Member] | Commercial Real Estate [Member] | Total Tdr Allowance [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance	8,088		1,542		8,088		1,542			6,567
Covered Loans [Member] | Commercial Real Estate Construction Financing Receivable [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	14,639		10,940		14,639		10,940			12,056
Covered Loans [Member] | Commercial Real Estate Construction Financing Receivable [Member] | Accruing TDRs [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Current	6,324		10,940		6,324		10,940			5,838
Delinquent	8,315		0		8,315		0			6,218
Total	14,639		10,940		14,639		10,940			12,056
Covered Loans [Member] | Commercial Real Estate Construction Financing Receivable [Member] | Nonaccruing TDRs [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Current	0		0		0		0			0
Delinquent	0		0		0		0			0
Total	0		0		0		0			0
Covered Loans [Member] | Commercial Real Estate Construction Financing Receivable [Member] | Total Tdr Allowance [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance	1,632		394		1,632		394			696
Covered Loans [Member] | Consumer Home Equity Lines Financing Receivable [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	4,742				4,742
Covered Loans [Member] | Consumer Home Equity Lines Financing Receivable [Member] | Accruing TDRs [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Current	4,698				4,698
Delinquent	44				44
Total	4,742				4,742
Covered Loans [Member] | Consumer Home Equity Lines Financing Receivable [Member] | Nonaccruing TDRs [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Current	0				0
Delinquent	0				0
Total	0				0
Covered Loans [Member] | Consumer Home Equity Lines Financing Receivable [Member] | Total Tdr Allowance [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance	0				0
Commercial Portfolio Segment [Member] | Noncovered Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance	39,159		30,338		39,159		30,338		40,327	32,363		28,366	29,764
Financing Receivable, Allowance for Credit Losses, Charge-offs	8,773		(4,528)		19,906		13,517
Financing Receivable, Allowance for Credit Losses, Recoveries	1,408		540		3,120		1,254
Financing Receivable, Allowance for Credit Losses, Provisions	6,197		5,960		23,582		12,837
Commercial Real Estate Portfolio Segment [Member] | Noncovered Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance	25,178		33,301		25,178		33,301		27,186	31,857		32,946	32,026
Financing Receivable, Allowance for Credit Losses, Charge-offs	727		(3,304)		3,496		7,763
Financing Receivable, Allowance for Credit Losses, Recoveries	180		6		825		54
Financing Receivable, Allowance for Credit Losses, Provisions	(1,461)		3,653		(4,008)		8,984
Commercial Construction Financing Receivable Portfolio Segment [Member] | Noncovered Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance	4,804		6,815		4,804		6,815		5,147	5,173		7,876	7,180
Financing Receivable, Allowance for Credit Losses, Charge-offs	127		(550)		165		3,245
Financing Receivable, Allowance for Credit Losses, Recoveries	61		171		364		545
Financing Receivable, Allowance for Credit Losses, Provisions	(277)		(682)		(568)		2,335
Finance Leases Portfolio Segment [Member] | Noncovered Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance	506		325		506		325		358	341		353	475
Financing Receivable, Allowance for Credit Losses, Charge-offs	0		(651)		0		778
Financing Receivable, Allowance for Credit Losses, Recoveries	0		1		38		35
Financing Receivable, Allowance for Credit Losses, Provisions	148		622		127		593
Installment Financing Receivable Portfolio Segment [Member] | Noncovered Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance	11,835		18,323		11,835		18,323		13,029	17,981		18,089	21,555
Financing Receivable, Allowance for Credit Losses, Charge-offs	5,507		(5,911)		14,441		20,204
Financing Receivable, Allowance for Credit Losses, Recoveries	2,883		3,375		9,104		10,812
Financing Receivable, Allowance for Credit Losses, Provisions	1,430		2,770		(809)		6,160
Home Equity Receivable Portfolio Segment [Member] | Noncovered Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance	4,885		6,243		4,885		6,243		5,449	6,766		7,142	7,217
Financing Receivable, Allowance for Credit Losses, Charge-offs	2,784		(2,779)		7,373		8,356
Financing Receivable, Allowance for Credit Losses, Recoveries	1,007		658		2,588		1,840
Financing Receivable, Allowance for Credit Losses, Provisions	1,213		1,222		2,904		5,542
Credit Card Receivables Portfolio Segment [Member] | Noncovered Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance	7,235		7,996		7,235		7,996		6,690	7,369		8,403	11,107
Financing Receivable, Allowance for Credit Losses, Charge-offs	1,390		(1,520)		4,618		6,135
Financing Receivable, Allowance for Credit Losses, Recoveries	488		585		1,583		1,789
Financing Receivable, Allowance for Credit Losses, Provisions	1,447		528		2,901		1,235
Residential Portfolio Segment [Member] | Noncovered Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance	5,340		5,846		5,340		5,846		5,663	5,849		6,012	5,366
Financing Receivable, Allowance for Credit Losses, Charge-offs	1,691		(771)		3,431		3,786
Financing Receivable, Allowance for Credit Losses, Recoveries	100		74		191		192
Financing Receivable, Allowance for Credit Losses, Provisions	$ 1,268		$ 531		$ 2,731		$ 4,074

[1] Excludes loss share receivable of $131.9 million as of September 30, 2012.

[2] Excludes loss share receivable of $220.5 million as of September 30, 2011

[3] Excludes loss share receivable of $205.7 million as of December 31, 2011.