Collateralized Securities Transactions	12 Months Ended
Dec. 31, 2017
Disclosure of Repurchase Agreements [Abstract]
Collateralized Securities Transactions	Collateralized Securities Transactions As discussed in Note 1, Piper Jaffray transitioned from a self clearing securities broker dealer to a fully disclosed clearing model in the third quarter of 2017. The Company's current short-term financing and prior customer securities activities involve the Company using securities as collateral. In the event that the counterparty did not meet its contractual obligation to return securities used as collateral (e.g., pursuant to the terms of a repurchase agreement), or customers did not deposit additional securities or cash for margin when required, the Company was exposed to the risk of reacquiring the securities or selling the securities at unfavorable market prices in order to satisfy its obligations. The Company controlled this risk by monitoring the market value of securities pledged or used as collateral on a daily basis and requiring adjustments in the event of excess market exposure. The Company uses unaffiliated third party custodians to administer the underlying collateral for certain of its short-term financings to mitigate risk. In a reverse repurchase agreement the Company purchases financial instruments from a seller, typically in exchange for cash, and agrees to resell the same or substantially the same financial instruments to the seller at a stated price plus accrued interest in the future. In a repurchase agreement, the Company sells financial instruments to a buyer, typically for cash, and agrees to repurchase the same or substantially the same financial instruments from the buyer at a stated price plus accrued interest at a future date. Even though repurchase and reverse repurchase agreements involve the legal transfer of ownership of financial instruments, they are accounted for as financing arrangements because they require the financial instruments to be repurchased or resold at maturity of the agreement. In a securities borrowed transaction, the Company borrows securities from a counterparty in exchange for cash. When the Company returns the securities, the counterparty returns the cash. Interest is generally paid periodically over the life of the transaction. Prior to transitioning to a fully disclosed clearing model, the Company obtained securities purchased under agreements to resell, securities borrowed and margin agreements on terms that permit it to repledge or resell the securities to others, typically pursuant to repurchase agreements. The Company obtained securities with a fair value of approximately $192.2 million at December 31, 2016, of which $185.2 million had been pledged or otherwise transferred to satisfy its commitments under financial instruments and other inventory positions sold, but not yet purchased. Reverse repurchase agreements, repurchase agreements and securities borrowed and loaned are reported on a net basis by counterparty when a legal right of offset exists. The Company had no outstanding securities lending arrangements as of December 31, 2017 or 2016. See Note 5 for information related to the Company's offsetting of derivative contracts.

Collateralized Securities Transactions

As discussed in Note 1, Piper Jaffray transitioned from a self clearing securities broker dealer to a fully disclosed clearing model in the third quarter of 2017.

The Company's current short-term financing and prior customer securities activities involve the Company using securities as collateral. In the event that the counterparty did not meet its contractual obligation to return securities used as collateral (e.g., pursuant to the terms of a repurchase agreement), or customers did not deposit additional securities or cash for margin when required, the Company was exposed to the risk of reacquiring the securities or selling the securities at unfavorable market prices in order to satisfy its obligations. The Company controlled this risk by monitoring the market value of securities pledged or used as collateral on a daily basis and requiring adjustments in the event of excess market exposure. The Company uses unaffiliated third party custodians to administer the underlying collateral for certain of its short-term financings to mitigate risk.

In a reverse repurchase agreement the Company purchases financial instruments from a seller, typically in exchange for cash, and agrees to resell the same or substantially the same financial instruments to the seller at a stated price plus accrued interest in the future. In a repurchase agreement, the Company sells financial instruments to a buyer, typically for cash, and agrees to repurchase the same or substantially the same financial instruments from the buyer at a stated price plus accrued interest at a future date. Even though repurchase and reverse repurchase agreements involve the legal transfer of ownership of financial instruments, they are accounted for as financing arrangements because they require the financial instruments to be repurchased or resold at maturity of the agreement.

In a securities borrowed transaction, the Company borrows securities from a counterparty in exchange for cash. When the Company returns the securities, the counterparty returns the cash. Interest is generally paid periodically over the life of the transaction.

Prior to transitioning to a fully disclosed clearing model, the Company obtained securities purchased under agreements to resell, securities borrowed and margin agreements on terms that permit it to repledge or resell the securities to others, typically pursuant to repurchase agreements. The Company obtained securities with a fair value of approximately $192.2 million at December 31, 2016, of which $185.2 million had been pledged or otherwise transferred to satisfy its commitments under financial instruments and other inventory positions sold, but not yet purchased.

Reverse repurchase agreements, repurchase agreements and securities borrowed and loaned are reported on a net basis by counterparty when a legal right of offset exists. The Company had no outstanding securities lending arrangements as of December 31, 2017 or 2016. See Note 5 for information related to the Company's offsetting of derivative contracts.