Commitments And Contingencies Commitments and Contingencies (Details) - Related party mortgage originator (with flow mortgage loan purchase and sale agreement) [Member] - Non-Exchange Traded Equity Investment in Mortgage Originator - USD ($)	Mar. 31, 2018	Dec. 31, 2017
Other Commitments [Line Items]
Guaranty Liabilities	$ 30,000,000
Drawn down amount being guaranteed	15,400,000
Guarantor Obligations, Current Carrying Value	$ 0	$ 0