Goodwill and Identifiable Intangible Assets (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Oct. 01, 2011	Oct. 01, 2010
Goodwill [Roll Forward]
Balance	$ 291,104,000	$ 291,104,000	$ 291,104,000
Insurance Division's fair value percentage of book value (in hundredths)				110.70%	104.60%
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	59,017,000	58,116,000
Accumulated Amortization	44,941,000	41,810,000
Net Carrying Amount	14,076,000	16,306,000
Remaining Weighted-Average Amortization Period (in years)	7.6
Amortization expense of identifiable intangible assets	3,100,000	3,500,000	4,000,000
Future amortization expense for identifiable intangible assets [Abstract]
2012	2,800,000
2013	2,500,000
2014	2,100,000
2015	1,800,000
2016	1,500,000
Core Deposit Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	45,309,000	44,408,000
Accumulated Amortization	35,730,000	33,662,000
Net Carrying Amount	9,579,000	10,746,000
Remaining Weighted-Average Amortization Period (in years)	7.6
Insurance Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	11,693,000	11,693,000
Accumulated Amortization	8,330,000	7,396,000
Net Carrying Amount	3,363,000	4,297,000
Remaining Weighted-Average Amortization Period (in years)	6.9
Banking Charters [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	1,325,000	1,325,000
Accumulated Amortization	546,000	480,000
Net Carrying Amount	779,000	845,000
Remaining Weighted-Average Amortization Period (in years)	11.7
Borrower Relationship Intangible [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	690,000	690,000
Accumulated Amortization	335,000	272,000
Net Carrying Amount	355,000	418,000
Remaining Weighted-Average Amortization Period (in years)	5.7
General Banking [Member]
Goodwill [Roll Forward]
Balance	246,736,000	246,736,000	246,736,000
Insurance [Member]
Goodwill [Roll Forward]
Balance	$ 44,368,000	$ 44,368,000	$ 44,368,000