Business Segment Information (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)	Jun. 30, 2015 USD ($) segment	Jun. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)
Business segment information
Number of reporting segments | segment			2
Revenue:
Total revenue	$ 396.0	$ 457.4	$ 749.5	$ 881.1
Operating Income:
Total operating income	31.6	35.4	46.8	56.0
Assets:
Total assets	1,820.4		1,820.4		$ 1,864.8
Eliminations
Revenue:
Total revenue	(1.0)	(5.5)	(2.5)	(10.5)
Corporate, eliminations and other
Operating Income:
Total operating income	0.3	(0.2)	0.8	1.1
Assets:
Total assets	(60.6)		(60.6)		(64.1)
BSI | Operating segments
Revenue:
Total revenue	366.2	421.5	693.7	815.4
Operating Income:
Total operating income	28.7	31.2	42.4	47.7
Assets:
Total assets	1,792.1		1,792.1		1,827.7
BEST | Operating segments
Revenue:
Total revenue	30.8	41.4	58.3	76.2
Operating Income:
Total operating income	2.6	$ 4.4	3.6	$ 7.2
Assets:
Total assets	$ 88.9		$ 88.9		$ 101.2