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Derivatives and Hedging Activities - Additional Information (Detail) | 9 Months Ended |  |
--- | --- | --- | ---
Sep. 30, 2017 USD ($) Contract $ / shares shares | Dec. 31, 2016 USD ($) shares | Dec. 01, 2016 USD ($)
Derivative [Line Items] |  |  |
Embedded Derivative, Fair Value of Embedded Derivative Asset | $ 18,190,000 |  | $ 10,800,000
Business Acquisitions, Purchase Price Allocation, Subsequent Years, Remaining Adjustments | $ 1,600,000 |  |
Preferred Stock, Shares Issued | shares | 867,846 |  |
Preferred Stock, Redemption Price Per Share | $ / shares | $ 50.00 |  |
Embedded Derivative, Gain (Loss) on Embedded Derivative, Net | $ 5,800,000 |  |
Credit Default Option [Member] |  |  |
Derivative [Line Items] |  |  |
Credit Risk Related Contingent Features Termination Value | 2,800,000 |  |
Net Liability Position [Member] |  |  |
Derivative [Line Items] |  |  |
Credit Risk Related Contingent Features Termination Value | 2,800,000 |  |
ERROR in label resolution. |  |  |
Derivative [Line Items] |  |  |
Fair Value of Credit Risk Derivatives | $ 2,600,000 |  |
Designated as Hedging Instrument [Member] | Interest Rate Caps |  |  |
Derivative [Line Items] |  |  |
Derivative, Number of Instruments Held | Contract | 2 |  |
Derivative, Notional Amount | $ 50,000,000 |  |
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative, Number of Instruments Held | Contract | 10 |  |
Derivative, Notional Amount | $ 550,000,000 |  |
Designated as Hedging Instrument [Member] | Interest Expense |  |  |
Derivative [Line Items] |  |  |
Change in fair value of interest rate derivatives included in AOCI and expected to be reclassified in the next 12 months | (80,500) |  |
Other Assets [Member] |  |  |
Derivative [Line Items] |  |  |
Interest Rate Cash Flow Hedge Asset at Fair Value | 2,000,000 | $ 2,400,000 |
Interest Rate Swap [Member] |  |  |
Derivative [Line Items] |  |  |
Fair market value of interest rate swaps | 7,600,000 | $ 2,600,000 |
Changes Measurement [Member] |  |  |
Derivative [Line Items] |  |  |
Embedded Derivative, Fair Value of Embedded Derivative Asset | $ 7,400,000 |  |
Parent Company [Member] |  |  |
Derivative [Line Items] |  |  |
Preferred Stock, Shares Issued | shares | 867,846 | 867,846 |
Interest Rate Cash Flow Hedge Asset at Fair Value | $ 2,000,000 | $ 2,400,000 |
Fair market value of interest rate swaps | $ 2,602,000 | $ 7,562,000 |

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- Definition Aggregate notional amount specified by the derivative(s). Expressed as an absolute value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 13 -Sentence Column B + Details
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- Definition Total remaining unamortized or unaccreted amounts of premiums, discounts, and intangible assets, in years subsequent to the year of acquisition, when the total amounts of remaining discounts, premiums, and intangible assets exceed 30 percent of stockholders' equity. + References No definition available. + Details
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- Definition Fair value of liability associated with financial asset or other 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. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=82849420&loc=SL20226003-175313 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4B -Subparagraph (a),(c) -URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624163-113959 + Details
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