Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Segment Reporting Information [Line Items]
Interest income	$ 2,520	$ 2,650	$ 7,826	$ 8,150
Interest expense	20,683	26,543	66,375	83,577
Provision for credit losses	2,000	6,000	10,000	26,000
Noninterest Income	46,698	29,112	123,026	93,429
Noninterest expense	89,408	86,620	265,664	266,515
Income before income taxes	30,598	11,328	75,933	24,300
Assets	9,472,437	9,175,874	9,472,437	9,175,874	9,193,237
Community Banking [Member]
Segment Reporting Information [Line Items]
Interest income	87,930	101,385	275,351	304,769
Interest expense	17,649	26,519	61,383	82,672
Net interest income	70,281	74,866	213,968	222,097
Provision for credit losses	1,980	6,000	9,980	26,056
Noninterest Income	8,033	11,459	45,808	56,618
Noninterest expense	61,552	70,353	202,455	229,747
Income before income taxes	14,782	9,972	47,341	22,912
Assets	9,466,908	9,154,384	9,466,908	9,154,384
Home Loan Division [Member]
Segment Reporting Information [Line Items]
Interest income	8,061	0	19,595	2,832
Interest expense	0	26	0	1,001
Net interest income	8,061	(26)	19,595	1,831
Provision for credit losses	20	0	20	(56)
Noninterest Income	38,816	17,649	77,517	36,297
Noninterest expense	31,784	16,267	66,548	36,768
Income before income taxes	15,073	1,356	30,544	1,416
Assets	4,633	21,490	4,633	21,490
Other and Eliminations [Member]
Segment Reporting Information [Line Items]
Interest income	0	(6)	0	(638)
Interest expense	3,034	(2)	4,992	(96)
Net interest income	(3,034)	(4)	(4,992)	(542)
Provision for credit losses	0	0	0	0
Noninterest Income	(151)	4	(299)	514
Noninterest expense	(3,928)	0	(3,339)	0
Income before income taxes	743	0	(1,952)	(28)
Assets	896	0	896	0
Reportable Segment [Member]
Segment Reporting Information [Line Items]
Interest income	95,991	101,379	294,946	306,963
Interest expense	20,683	26,543	66,375	83,577
Net interest income	75,308	74,836	228,571	223,386
Provision for credit losses	2,000	6,000	10,000	26,000
Noninterest Income	46,698	29,112	123,026	93,429
Noninterest expense	89,408	86,620	265,664	266,515
Income before income taxes	$ 30,598	$ 11,328	$ 75,933	$ 24,300