Fair Value Measurements Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) (Fair Value, Measurements, Recurring [Member], USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Level 1 [Member]
Mortgages Held-for-sale, Fair Value Disclosure	$ 0	$ 0
Available-for-sale Securities, Fair Value Disclosure	44,113	34,586
Other Assets, Fair Value Disclosure	15,797	15,292
Assets, Fair Value Disclosure	59,910	49,878
Liabilities, Fair Value Disclosure	15,420	15,721
Level 1 [Member] | Equity Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	44,113	34,586
Level 1 [Member] | U.S. Government Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	0	0
Level 1 [Member] | U.S. Government-Sponsored Agency Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	0	0
Level 1 [Member] | State and Municipal Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	0	0
Level 1 [Member] | Corporate Debt Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	0	0
Level 1 [Member] | Collateralized Mortgage Obligations [Member]
Available-for-sale Securities, Fair Value Disclosure	0	0
Level 1 [Member] | Mortgage-Backed Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	0	0
Level 1 [Member] | Auction Rate Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	0	0
Level 2 [Member]
Mortgages Held-for-sale, Fair Value Disclosure	85,477	47,009
Available-for-sale Securities, Fair Value Disclosure	2,504,053	2,321,748
Other Assets, Fair Value Disclosure	20,079	6,645
Assets, Fair Value Disclosure	2,609,609	2,375,402
Liabilities, Fair Value Disclosure	14,995	5,478
Level 2 [Member] | Equity Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	0	0
Level 2 [Member] | U.S. Government Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	326	334
Level 2 [Member] | U.S. Government-Sponsored Agency Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	2,440	4,073
Level 2 [Member] | State and Municipal Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	308,032	322,018
Level 2 [Member] | Corporate Debt Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	97,875	114,017
Level 2 [Member] | Collateralized Mortgage Obligations [Member]
Available-for-sale Securities, Fair Value Disclosure	1,030,190	1,001,209
Level 2 [Member] | Mortgage-Backed Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	1,065,190	880,097
Level 2 [Member] | Auction Rate Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	0	0
Level 3 [Member]
Mortgages Held-for-sale, Fair Value Disclosure	0	0
Available-for-sale Securities, Fair Value Disclosure	168,313	234,500
Other Assets, Fair Value Disclosure	0	0
Assets, Fair Value Disclosure	168,313	234,500
Liabilities, Fair Value Disclosure	0	0
Level 3 [Member] | Equity Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	0	0
Level 3 [Member] | U.S. Government Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	0	0
Level 3 [Member] | U.S. Government-Sponsored Agency Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	0	0
Level 3 [Member] | State and Municipal Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	0	0
Level 3 [Member] | Corporate Debt Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	8,251	9,289
Level 3 [Member] | Collateralized Mortgage Obligations [Member]
Available-for-sale Securities, Fair Value Disclosure	0	0
Level 3 [Member] | Mortgage-Backed Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	0	0
Level 3 [Member] | Auction Rate Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	160,062	225,211
Total [Member]
Mortgages Held-for-sale, Fair Value Disclosure	85,477	47,009
Available-for-sale Securities, Fair Value Disclosure	2,716,479	2,590,834
Other Assets, Fair Value Disclosure	35,876	21,937
Assets, Fair Value Disclosure	2,837,832	2,659,780
Liabilities, Fair Value Disclosure	30,415	21,199
Total [Member] | Equity Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	44,113	34,586
Total [Member] | U.S. Government Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	326	334
Total [Member] | U.S. Government-Sponsored Agency Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	2,440	4,073
Total [Member] | State and Municipal Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	308,032	322,018
Total [Member] | Corporate Debt Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	106,126	123,306
Total [Member] | Collateralized Mortgage Obligations [Member]
Available-for-sale Securities, Fair Value Disclosure	1,030,190	1,001,209
Total [Member] | Mortgage-Backed Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	1,065,190	880,097
Total [Member] | Auction Rate Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	$ 160,062	$ 225,211