Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Segment Reporting Information [Line Items]
Interest income	$ 96,444	$ 95,991	$ 281,218	$ 294,946
Interest expense	13,896	20,683	41,362	66,375
Net interest income	82,548	75,308	239,856	228,571
Provision for credit losses	0	2,000	0	10,000
Noninterest Income	31,890	46,698	111,459	123,026
Noninterest expense	85,334	89,408	248,941	265,664
Income before income taxes	29,104	30,598	102,374	75,933
Assets	9,984,336	9,472,437	9,984,336	9,472,437	9,236,910
Community Banking [Member]
Segment Reporting Information [Line Items]
Interest income	89,430	87,930	259,819	275,351
Interest expense	12,427	17,649	36,988	61,383
Net interest income	77,003	70,281	222,831	213,968
Provision for credit losses	0	1,980	0	9,980
Noninterest Income	15,756	8,033	54,757	45,808
Noninterest expense	64,074	61,552	182,433	202,455
Income before income taxes	28,685	14,782	95,155	47,341
Assets	9,758,046	9,466,908	9,758,046	9,466,908
Home Loan Division [Member]
Segment Reporting Information [Line Items]
Interest income	7,014	8,061	21,399	19,595
Interest expense	0	0	0	0
Net interest income	7,014	8,061	21,399	19,595
Provision for credit losses	0	20	0	20
Noninterest Income	16,134	38,816	57,167	77,517
Noninterest expense	17,468	31,784	61,278	66,548
Income before income taxes	5,680	15,073	17,288	30,544
Assets	200,575	4,633	200,575	4,633
Intersegment Elimination [Member]
Segment Reporting Information [Line Items]
Interest income	0	0	0	0
Interest expense	1,469	3,034	4,374	4,992
Net interest income	(1,469)	(3,034)	(4,374)	(4,992)
Provision for credit losses	0	0	0	0
Noninterest Income	0	(151)	(465)	(299)
Noninterest expense	3,792	(3,928)	5,230	(3,339)
Income before income taxes	(5,261)	743	(10,069)	(1,952)
Assets	$ 25,715	$ 896	$ 25,715	$ 896