Business Segment Information (Details) $ in Millions	3 Months Ended
	Mar. 31, 2016 USD ($) segment	Mar. 31, 2015 USD ($)	Dec. 31, 2015 USD ($)
Business segment information
Number of reportable segments | segment	2
Revenue:
Total revenue	$ 375.4	$ 353.5
Operating Income:
Total operating income	34.0	15.2
Assets:
Total assets	1,739.8		$ 1,730.0
Eliminations
Revenue:
Total revenue	(2.2)	(1.5)
Corporate, eliminations and other
Operating Income:
Total operating income	1.0	0.5
Assets:
Total assets	(60.4)		(63.5)
BSI | Operating segments
Revenue:
Total revenue	350.4	327.5
Operating Income:
Total operating income	33.0	13.7
Assets:
Total assets	1,720.3		1,714.4
BEST | Operating segments
Revenue:
Total revenue	27.2	27.5
Operating Income:
Total operating income		$ 1.0
Assets:
Total assets	$ 79.9		$ 79.1