Subsequent Event Subsequent Event (Details) $ in Millions	Jun. 30, 2017 USD ($)
Subsequent Event [Line Items]
Optional increase in borrowing availability	$ 25.0
Maximum borrowing availability, subject to obtaining additional commitments	500.0
Minimum Tangible Net Worth	465.2
First Amendment to New Unsecured Credit Facility [Member]
Subsequent Event [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	400.0
Second Amendment to Credit Facility [Member]
Subsequent Event [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 475.0
Maximum [Member] | First Amendment to New Unsecured Credit Facility [Member]
Subsequent Event [Line Items]
Basis Points Spread on Variable Rate - Credit Facility	250