Business Segment Information (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) segment	Sep. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)
Business segment information
Number of reporting segments | segment			2
Revenue:
Total revenue	$ 396.1	$ 419.8	$ 1,145.6	$ 1,300.9
Operating Income:
Total operating income	28.2	4.9	75.0	60.9
Assets:
Total assets	1,842.9		1,842.9		$ 1,864.8
Eliminations
Revenue:
Total revenue	(3.4)	(3.6)	(5.9)	(14.1)
Corporate, eliminations and other
Operating Income:
Total operating income	(0.1)	0.2	0.7	1.3
Assets:
Total assets	(63.5)		(63.5)		(64.1)
BSI | Operating segments
Revenue:
Total revenue	366.6	383.4	1,060.3	1,198.8
Operating Income:
Total operating income	25.8	0.8	68.2	48.5
Assets:
Total assets	1,821.2		1,821.2		1,827.7
BEST | Operating segments
Revenue:
Total revenue	32.9	40.0	91.2	116.2
Operating Income:
Total operating income	2.5	$ 3.9	6.1	$ 11.1
Assets:
Total assets	$ 85.2		$ 85.2		$ 101.2