Principles of Consolidation (Fair Value Measurement) (Details) - Fair Value, Measurements, Recurring [Member] $ in Millions	Jun. 30, 2017 USD ($)
Quoted prices in active market (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Restricted amounts held in escrow-current	$ 54.0
Total assets at fair value	54.0
Significant other observable inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Restricted amounts held in escrow-current	0.0
Total assets at fair value	0.0
Significant unobservable inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Restricted amounts held in escrow-current	0.0
Total assets at fair value	0.0
Carrying (Reported) Amount, Fair Value Disclosure [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Restricted amounts held in escrow-current	54.0
Total assets at fair value	$ 54.0