SEGMENT INFORMATION AND CONCENTRATION OF CREDIT RISK - Segment Assets (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Revenues from External Customers and Long-Lived Assets [Line Items]
Deferred tax assets	$ 28.1	$ 29.7
Total Assets	2,209.1	1,990.9
Unallocated: [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Cash and cash equivalents, including current restricted cash	59.0	83.8
Deferred tax assets	28.1	29.7
Other assets, including long-term restricted investments	39.6	37.7
Operating Segments [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total Assets	2,082.4	1,839.7
Operating Segments [Member] | AQH [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total Assets	585.7	610.7
Operating Segments [Member] | SCS [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total Assets	339.6	327.7
Operating Segments [Member] | ERG [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total Assets	365.0	378.4
Operating Segments [Member] | RCH [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total Assets	538.2	175.0
Operating Segments [Member] | CAS [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total Assets	190.7	199.0
Operating Segments [Member] | AVC [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total Assets	$ 63.2	$ 148.9