Business Segments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Schedule of segment reporting information by segment
Interest income, including loan fees									$ 269,720	$ 317,289	$ 310,759
Total interest income									269,720	317,289	310,759
Interest Expense									35,039	57,972	88,495
Charge for funds used									0
Total interest expense									35,039	57,972	88,495
Net interest income	55,197	55,980	62,395	57,109	59,149	62,615	64,214	73,339	234,681	259,317	222,264
Provision for credit losses				7,068	12,700	25,300	11,000	12,200	7,068	61,200	80,500
Net interest income after provision for credit losses									227,613	198,117	141,764
Other operating income									34,216	57,114	81,071
Other operating expense									141,025	168,492	133,586
Segment pretax profit (loss)									120,804	86,739	89,249
Segment assets	6,482,915				6,436,691				6,482,915	6,436,691	6,739,769
Business Financial Centers [Member]
Schedule of segment reporting information by segment
Interest income, including loan fees									157,376	170,335	159,347
Credit for funds provided									24,811	71,752	53,759
Total interest income									182,187	242,087	213,106
Interest Expense									10,411	22,438	28,428
Charge for funds used									4,884	11,743	12,559
Total interest expense									15,295	34,181	40,987
Net interest income									166,892	207,906	172,119
Net interest income after provision for credit losses									166,892	207,906	172,119
Other operating income									21,622	23,204	19,537
Other operating expense									49,802	51,922	47,860
Segment pretax profit (loss)									138,712	179,188	143,796
Segment assets	5,003,093				4,941,548				5,003,093	4,941,548	4,696,134
Treasury [Member]
Schedule of segment reporting information by segment
Interest income, including loan fees									62,732	76,651	104,778
Total interest income									62,732	76,651	104,778
Interest Expense									21,258	32,302	55,572
Charge for funds used									35,128	41,484	28,077
Total interest expense									56,386	73,786	83,649
Net interest income									6,346	2,865	21,129
Net interest income after provision for credit losses									6,346	2,865	21,129
Other operating income									(655)	37,997	28,124
Other operating expense									4,117	20,125	5,945
Segment pretax profit (loss)									1,574	20,737	43,308
Segment assets	2,650,201				2,329,344				2,650,201	2,329,344	2,276,909
Other [Member]
Schedule of segment reporting information by segment
Interest income, including loan fees									49,612	70,303	46,634
Credit for funds provided									39,621	28,965	23,233
Total interest income									89,233	99,268	69,867
Interest Expense									3,370	3,232	4,495
Charge for funds used									24,420	47,490	36,356
Total interest expense									27,790	50,722	40,851
Net interest income									61,443	48,546	29,016
Provision for credit losses									7,068	61,200	80,500
Net interest income after provision for credit losses									54,375	(12,654)	(51,484)
Other operating income									13,249	(4,087)	33,410
Other operating expense									87,106	96,445	79,781
Segment pretax profit (loss)									(19,482)	(113,186)	(97,855)
Segment assets	689,710				630,451				689,710	630,451	698,351
Eliminations [Member]
Schedule of segment reporting information by segment
Credit for funds provided									(64,432)	(100,717)	(76,992)
Total interest income									(64,432)	(100,717)	(76,992)
Charge for funds used									(64,432)	(100,717)	(76,992)
Total interest expense									(64,432)	(100,717)	(76,992)
Segment assets	$ (1,860,089)				$ (1,464,652)				$ (1,860,089)	$ (1,464,652)	$ 931,625