Investments	12 Months Ended
Dec. 31, 2018
Equity Method Investments and Joint Ventures [Abstract]
Investments	Investments Our equity investments, including our investments in Euroclear plc, or Euroclear, BIDS Trading, L.P. and Coinbase Global, Inc., or Coinbase, among others, are now subject to valuation under ASU 2016-01. Investment in Euroclear During 2017, we purchased a 4.7% stake in Euroclear valued at €276 million ($327 million). Upon purchasing this stake, we agreed to participate on the Euroclear Board of Directors. During the same period, we negotiated an additional purchase which closed on February 21, 2018 following regulatory approval. This provided us with an additional 5.1% stake in Euroclear for a purchase price of €246 million in cash ($304 million). As of December 31, 2018, we own a 9.8% stake in Euroclear for a total investment of $631 million. Euroclear is classified as an equity investment and included as an other non-current asset in our consolidated balance sheets. Euroclear is a provider of post-trade services, including settlement, central securities depositories and related services for cross-border transactions across asset classes. In 2018, we recognized dividend income of $15 million from Euroclear, included in other income. Investment in Cetip Until March 29, 2017, we held a 12% ownership interest in Cetip, S.A., or Cetip, classified as a long-term investment. On that date, in connection with the merger of Cetip with BM&FBOVESPA S.A., which changed its name to B3 S.A. - Brasil, Bolsa, Balcão, or B3, we recognized a $176 million realized investment gain in other income (expense), net, and $9 million in foreign exchange losses and transaction expenses in other income (expense), net. We recognized dividend income received relating to our investment in Cetip in other income of $5 million and $17 million in 2017 and 2016, respectively. Other Investments We had previously accounted for our investment in MERS as an equity method investment before completing our acquisition of 100% of MERS on October 3, 2018 (Note 3). As of December 31, 2018, our Options Clearing Corporation, or OCC, investment is our sole equity method investment and is included in other non-current assets in the accompanying consolidated balance sheets. We recognized $46 million, $36 million and $25 million in income related to these equity method investments during 2018, 2017 and 2016, respectively, as other income. See “Summary of Significant Accounting Policies” for further information on our equity method investments. As a result of our acquisition of a majority equity position in MERS in June 2016, MERS was required to have cash or investments reserved in order to satisfy terms of the governing agreements of the acquisition. The reserve is satisfied with fixed income securities, including treasuries, corporates and municipals. The balance of the reserve is primarily used to cover settlement amounts from all litigation and claims arising from the operations of MERS prior to the acquisition of the majority equity position. As of December 31, 2018, and subsequent to our October 2018 acquisition and consolidation of the remaining MERS interests, it amounted to $81 million and is included in prepaid expenses and other current assets and non-current assets. As of December 31, 2018, the reserve is offset by an equal $81 million due to former MERS equity holders and is reflected in other current liabilities and other non-current liabilities.

Investments

Our equity investments, including our investments in Euroclear plc, or Euroclear, BIDS Trading, L.P. and Coinbase Global, Inc., or Coinbase, among others, are now subject to valuation under ASU 2016-01.

Investment in Euroclear

During 2017, we purchased a 4.7% stake in Euroclear valued at €276 million ($327 million). Upon purchasing this stake, we agreed to participate on the Euroclear Board of Directors. During the same period, we negotiated an additional purchase which closed on February 21, 2018 following regulatory approval. This provided us with an additional 5.1% stake in Euroclear for a purchase price of €246 million in cash ($304 million). As of December 31, 2018, we own a 9.8% stake in Euroclear for a total investment of $631 million. Euroclear is classified as an equity investment and included as an other non-current asset in our consolidated balance sheets.

Euroclear is a provider of post-trade services, including settlement, central securities depositories and related services for cross-border transactions across asset classes. In 2018, we recognized dividend income of $15 million from Euroclear, included in other income.

Investment in Cetip

Until March 29, 2017, we held a 12% ownership interest in Cetip, S.A., or Cetip, classified as a long-term investment. On that date, in connection with the merger of Cetip with BM&FBOVESPA S.A., which changed its name to B3 S.A. - Brasil, Bolsa, Balcão, or B3, we recognized a $176 million realized investment gain in other income (expense), net, and $9 million in foreign exchange losses and transaction expenses in other income (expense), net. We recognized dividend income received relating to our investment in Cetip in other income of $5 million and $17 million in 2017 and 2016, respectively.

Other Investments

We had previously accounted for our investment in MERS as an equity method investment before completing our acquisition of 100% of MERS on October 3, 2018 (Note 3). As of December 31, 2018, our Options Clearing Corporation, or OCC, investment is our sole equity method investment and is included in other non-current assets in the accompanying consolidated balance sheets. We recognized $46 million, $36 million and $25 million in income related to these equity method investments during 2018, 2017 and 2016, respectively, as other income. See “Summary of Significant Accounting Policies” for further information on our equity method investments.

As a result of our acquisition of a majority equity position in MERS in June 2016, MERS was required to have cash or investments reserved in order to satisfy terms of the governing agreements of the acquisition. The reserve is satisfied with fixed income securities, including treasuries, corporates and municipals. The balance of the reserve is primarily used to cover settlement amounts from all litigation and claims arising from the operations of MERS prior to the acquisition of the majority equity position. As of December 31, 2018, and subsequent to our October 2018 acquisition and consolidation of the remaining MERS interests, it amounted to $81 million and is included in prepaid expenses and other current assets and non-current assets. As of December 31, 2018, the reserve is offset by an equal $81 million due to former MERS equity holders and is reflected in other current liabilities and other non-current liabilities.