Commitments and Contingencies - Schedule of Limited Partners' Callable Commitments (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Limited Partners' Capital Account [Line Items]
Callable commitments amount	$ 61.1	$ 101.0
Taconic New York City GP Fund
Limited Partners' Capital Account [Line Items]
Callable commitments amount	13.7	26.0
LCS SHIP Venture I, LLC
Limited Partners' Capital Account [Line Items]
Callable commitments amount	$ 47.4	$ 75.0