Fair Value Measurements - Narrative (Details) - USD ($)	6 Months Ended
Jun. 30, 2017	Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Auction Rate Securities Committed To Purchase related to settlements with regulators	$ 5,000,000
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	4,130,000	$ 2,024,000
Derivative Liability, Notional Amount	4,663,277,000	4,756,631,000
Principal	124,188,000
Amount Of Auction Rate Securities Firm Purchased And Hold Net of Redemptions	109,200,000
Auction Rate Securities Committed To Purchase From Clients under Legal Settlements and Awards	10,000,000
Securities purchased under agreements to resell, fair value	3,617,000	$ 24,006,000
Fair Value Of Securities Repurchase Agreement	0
Valuation adjustment (unrealized loss) for ARS	$ (2,309,000)
Forward or delayed delivery of the underlying instrument with settlement (in days)	180 days
Fair Value Of Level Three Assets	$ 121,879,000
Auction Rate Preferred Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
U S Treasury Rate	1.72%
Student Loan Auction Rate Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
U S Treasury Rate	2.14%
Maximum [Member] \| LIBOR or Treasury Yield [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Auction market preferred securities variable interest rate earned	200.00%
Auction Rate Securities [Member] \| Maximum [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commitment to purchase ARS period maximum	2020
Auction Rate Securities Purchase Commitment [Member] \| Municipal Auction Rate Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Principal	$ 2,000
Valuation adjustment (unrealized loss) for ARS	0
Fair Value Of Level Three Assets	$ 2,000
Valuation Technique	Secondary Market Trading Activity
Auction Rate Securities Purchase Commitment [Member] \| Student Loan Auction Rate Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Principal	$ 24,000
Valuation adjustment (unrealized loss) for ARS	(1,000)
Fair Value Of Level Three Assets	$ 23,000
Valuation Technique	Discounted Cash Flow
Auction Rate Securities Purchase Commitment [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Principal	$ 14,963,000
Valuation adjustment (unrealized loss) for ARS	(254,000)
Fair Value Of Level Three Assets	14,709,000
Auction Rate Securities Purchase Commitment [Member] \| Auction Rate Preferred Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Principal	$ 14,937,000
Duration	4 years
Valuation adjustment (unrealized loss) for ARS	$ (253,000)
Fair Value Of Level Three Assets	$ 14,684,000
Valuation Technique	Discounted Cash Flow
Auction Rate Securities Purchase Commitment [Member] \| Student Loan Auction Rate Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Current Yield	2.51%
Permanent and construction loans , discount rate	3.34%
Duration	7 years
Auction Rate Securities Purchase Commitment [Member] \| Weighted Average [Member] \| Auction Rate Preferred Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Current Yield	1.68%
Permanent and construction loans , discount rate	2.17%
Duration	4 years
Auction Rate Securities Purchase Commitment [Member] \| Weighted Average [Member] \| Student Loan Auction Rate Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Current Yield	2.51%
Permanent and construction loans , discount rate	3.34%
Duration	7 years
Auction Rate Securities Purchase Commitment [Member] \| Maximum [Member] \| Auction Rate Preferred Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Current Yield	1.93%
Permanent and construction loans , discount rate	2.58%
Auction Rate Securities Purchase Commitment [Member] \| Minimum [Member] \| Auction Rate Preferred Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Current Yield	1.50%
Permanent and construction loans , discount rate	1.89%
Auction Rate Securities Owned [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Principal	$ 109,225,000
Valuation adjustment (unrealized loss) for ARS	(2,055,000)
Fair Value Of Level Three Assets	107,170,000
Auction Rate Securities Owned [Member] \| Auction Rate Preferred Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Principal	$ 108,900,000
Duration	4 years
Valuation adjustment (unrealized loss) for ARS	$ (2,037,000)
Fair Value Of Level Three Assets	$ 106,863,000
Valuation Technique	Discounted Cash Flow
Auction Rate Securities Owned [Member] \| Student Loan Auction Rate Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Current Yield	2.51%
Principal	$ 300,000
Permanent and construction loans , discount rate	3.34%
Duration	7 years
Valuation adjustment (unrealized loss) for ARS	$ (15,000)
Fair Value Of Level Three Assets	$ 285,000
Valuation Technique	Discounted Cash Flow
Auction Rate Securities Owned [Member] \| Weighted Average [Member] \| Auction Rate Preferred Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Current Yield	1.68%
Permanent and construction loans , discount rate	2.17%
Duration	4 years
Auction Rate Securities Owned [Member] \| Weighted Average [Member] \| Student Loan Auction Rate Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Current Yield	2.51%
Permanent and construction loans , discount rate	3.34%
Duration	7 years
Auction Rate Securities Owned [Member] \| Maximum [Member] \| Auction Rate Preferred Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Current Yield	1.93%
Permanent and construction loans , discount rate	2.58%
Auction Rate Securities Owned [Member] \| Minimum [Member] \| Auction Rate Preferred Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Current Yield	1.50%
Permanent and construction loans , discount rate	1.89%
Fair Value, Valuation Scenario Two [Member] \| Auction Rate Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Change in discount rate	50.00%
Decrease in fair value of ARS	$ 2,300,000
Fair Value, Valuation Scenario One [Member] \| Auction Rate Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Change in discount rate	25.00%
Decrease in fair value of ARS	$ 1,200,000

Amount Of Auction Rate Securities Firm Purchased And Hold Net of Redemptions

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Auction Rate Securities Committed To Purchase From Clients under Legal Settlements and Awards

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Auction Rate Securities Committed To Purchase related to settlements with regulators

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Fair value of the level 3 assets used for the quantitative disclosure.

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Fair value of securities repurchase agreement.

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Fair Value Of Securities Reverse Repurchase Agreement

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Fair value unobservable input current yield.

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Fair value unobservable inputs duration.

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Amount represents the principal amount of the level 3 assets used for the quantitative disclosure.

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Maximum settlement period in case of delayed delivery of underlying instrument.

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Securities committed to purchase period.

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Sensitivity analysis of fair value of interests continued to be held by transferor servicing assets or liabilities change in discount rate.

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Specific period of US Treasury rate as of reporting period.

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Valuation adjustment for the level 3 assets used for quantitative disclosure.

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The interest (or dividend) rates earned on action market preferred securities (on an annual basis or APY) for the period reported.

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Fair value, after offset of derivative asset, of financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, elected not to be and before offset against a right to receive collateral under a master netting arrangement. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

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Nominal or face amount used to calculate payments on the derivative liability.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Interest rate used to find the present value of an amount to be paid or received in the future as an input to measure fair value. For example, but not limited to, weighted average cost of capital (WACC), cost of capital, cost of equity and cost of debt.

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The hypothetical financial impact of a specified adverse percentage change in discount rate on the fair value of transferor's interests in transferred financial assets (including any servicing assets or servicing liabilities) as of the balance sheet date.

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