Fair Value Measurements Fair Value Measurements, Financial Instruments Measured On a Recurring Basis, Quantitative Information (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available for sale securities	$ 10,147,162		$ 11,287,221
Municipal and other tax-exempt securities [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available for sale securities	73,775		87,142
Other debt securities [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available for sale securities	35,241		36,389
Fair Value, Inputs, Level 3 [Member] | Available for sale Securities [Member] | Municipal and other tax-exempt securities [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Asset, Par Value			45,570
Fair Value Inputs, Asset, Amortized Cost			40,857	[1]
Fair Value Inputs, Asset, Fair Value			40,702
Fair Value, Inputs, Level 3 [Member] | Available for sale Securities [Member] | Municipal and other tax-exempt securities [Member] | External Credit Rating, Investment Grade [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Asset, Par Value	18,695		28,570
Fair Value Inputs, Asset, Amortized Cost	18,624		28,473	[1]
Fair Value Inputs, Asset, Fair Value	17,805		28,318
Fair Value Measurements, Valuation Techniques	Discounted cash flows	[2]	Discounted cash flows	[2]
Fair Value Measurements, Significant Unobservable Input	Interest rate spread		Interest rate spread
Fair Value Inputs, Assets, Discount Rate, Minimum	4.97%	[3]	1.00%	[4]
Fair Value Inputs, Assets, Discount Rate, Maximum	5.27%	[3]	1.50%	[4]
Fair Value Inputs, Assets, Discount Rate, Weighted Average	5.16%	[3]	1.25%	[4]
Fair Value Inputs, Assets, Fair Value As Percentage of Par Value, Minimum	95.02%	[5]	98.83%	[5]
Fair Value Inputs, Assets, Fair Value As Percentage of Par Value, Maximum	95.50%	[5]	99.43%	[5]
Fair Value Inputs, Fair Value As Percentage of Par Value, Weighted Average	95.24%	[5]	99.12%	[5]
Investment Grade Tax Exempt Securities Yield Spread Over Comparable Securities Minimum	467		75
Investment Grade Tax Exempt Securities Yield Spread Over Comparable Securities Maximum	518		80
Additional Decrease in Fair Value From a 100 Basis Point Increase in Interest Rate Spread	(172)
Fair Value, Inputs, Level 3 [Member] | Available for sale Securities [Member] | Municipal and other tax-exempt securities [Member] | External Credit Rating, Non Investment Grade [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Asset, Par Value			17,000
Fair Value Inputs, Asset, Amortized Cost			12,384	[1]
Fair Value Inputs, Asset, Fair Value			12,384
Fair Value Measurements, Valuation Techniques			Discounted cash flows	[2]
Fair Value Measurements, Significant Unobservable Input			Interest rate spread
Fair Value Inputs, Assets, Discount Rate, Minimum			7.21%
Fair Value Inputs, Assets, Discount Rate, Maximum			9.83%
Fair Value Inputs, Assets, Discount Rate, Weighted Average			7.82%
Fair Value Inputs, Assets, Fair Value As Percentage of Par Value, Minimum			72.79%	[5]
Fair Value Inputs, Assets, Fair Value As Percentage of Par Value, Maximum			73.00%	[5]
Fair Value Inputs, Fair Value As Percentage of Par Value, Weighted Average			72.85%	[5]
Below Investment Grade Tax Exempt Securities Yield Spread Over Comparable Securities			700
Fair Value, Inputs, Level 3 [Member] | Available for sale Securities [Member] | Other debt securities [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Asset, Par Value	4,900		5,400
Fair Value Inputs, Asset, Amortized Cost	4,900		5,400	[1]
Fair Value Inputs, Asset, Fair Value	4,712		5,399
Fair Value Measurements, Valuation Techniques	Discounted cash flows	[2]	Discounted cash flows	[2]
Fair Value Measurements, Significant Unobservable Input	Interest rate spread		Interest rate spread
Fair Value Inputs, Assets, Discount Rate, Minimum	5.67%	[6]	1.65%	[7]
Fair Value Inputs, Assets, Discount Rate, Maximum	5.67%	[6]	1.71%	[7]
Fair Value Inputs, Assets, Discount Rate, Weighted Average	5.67%	[6]	1.70%	[7]
Fair Value Inputs, Assets, Fair Value As Percentage of Par Value, Minimum	96.16%	[5]	100.00%	[5]
Fair Value Inputs, Assets, Fair Value As Percentage of Par Value, Maximum	96.16%	[5]	100.00%	[5]
Fair Value Inputs, Fair Value As Percentage of Par Value, Weighted Average	96.16%	[5]	100.00%	[5]
Average Yields On Comparable Short-term Taxable Securities Maximum	1.00%		1.00%
Additional Decrease in Fair Value From a 100 Basis Point Increase in Interest Rate Spread	(36)
Fair Value, Inputs, Level 3 [Member] | Available for sale Securities [Member] | Equity securities and mutual funds [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Asset, Amortized Cost	2,420		2,420
Available for sale securities	$ 4,207		$ 2,161
Fair Value Measurements, Valuation Techniques	Publicly announced preliminary purchase price information from acquirer.	[2]	Tangible book value per share of publicly traded financial institutions of similar size, less liquidity discount.
Fair Value Measurements, Significant Unobservable Input	Discount for settlement uncertainty.		Peer group tangible book per share and liquidity discount
Fair Value Inputs, Assets, Liquidity Discount			20.00%
Fair Value, Inputs, Level 3 [Member] | Other assets - private equity funds [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Measurements, Valuation Techniques	Net asset value reported by underlying fund		Net asset value reported by underlying fund
Fair Value Measurements, Significant Unobservable Input	Net asset value reported by underlying fund		Net asset value reported by underlying fund

[1] Amortized cost reduced by other-than-temporary impairments recorded in earnings. See Note 2 for additional discussion.

[2] Discounted cash flows developed using discount rates primarily based on reference to interest rate spreads for comparable securities of similar duration and credit rating as determined by the nationally-recognized rating agencies, adjusted for lack of trading volume

[3] Interest rate yields used to value investment grade tax-exempt securities represent a spread of 467 to 518 basis points over average yields for comparable tax-exempt securities.

[4] Interest rate yields used to value investment grade tax-exempt securities represent a spread of 75 to 80 basis points over average yields for comparable tax-exempt securities.

[5] Represents fair value as a percentage of par value

[6] Fair value of shares of a smaller privately-held financial institution were valued using preliminary announced purchase information by a publicly-traded acquirer.

[7] Interest rate yields used to value investment grade taxable securities based on comparable short-term taxable securities which are generally yielding less than 1%.