CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) shares in Millions, $ in Millions	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Retained Earnings
Balance (in shares) at Dec. 31, 2014		77.4
Balance at Dec. 31, 2014	$ 1,013.3	$ 77.4	$ 788.3	$ (443.1)	$ 590.7
Net income (loss)	(1.4)	0.0	0.0	0.0	(1.4)
Other comprehensive income (loss)	(49.4)	0.0	0.0	(49.4)	0.0
Dividends paid:
Common stock ($0.80 per share)	$ (79.5)	$ 0.0	0.0	0.0	(79.5)
Common stock issued for:
Stock options exercised (in shares)	0.1	0.1
Stock options exercised	$ 3.1	$ 0.1	3.0	0.0	0.0
Other transactions (in shares)		0.1
Other transactions	2.3	$ 0.1	2.2	0.0	0.0
Business acquired in purchase transaction, net of issuance costs (in shares)		87.5
Business acquired in purchase transaction, net of issuance costs	1,525.5	$ 87.5	1,438.0	0.0	0.0
Stock-based compensation	4.9	$ 0.0	4.9	0.0	0.0
Balance (in shares) at Dec. 31, 2015		165.1
Balance at Dec. 31, 2015	2,418.8	$ 165.1	2,236.4	(492.5)	509.8
Net income (loss)	(3.9)	0.0	0.0	0.0	(3.9)
Other comprehensive income (loss)	(17.5)	0.0	0.0	(17.5)	0.0
Dividends paid:
Common stock ($0.80 per share)	$ (132.1)	$ 0.0	0.0	0.0	(132.1)
Common stock issued for:
Stock options exercised (in shares)	0.3	0.3
Stock options exercised	$ 4.1	$ 0.3	3.8	0.0	0.0
Other transactions (in shares)		0.0
Other transactions	(0.8)	$ 0.0	(0.8)	0.0	0.0
Stock-based compensation	4.4	$ 0.0	4.4	0.0	0.0
Balance (in shares) at Dec. 31, 2016		165.4
Balance at Dec. 31, 2016	2,273.0	$ 165.4	2,243.8	(510.0)	373.8
Net income (loss)	549.5	0.0	0.0	0.0	549.5
Other comprehensive income (loss)	25.4	0.0	0.0	25.4	0.0
Dividends paid:
Common stock ($0.80 per share)	$ (133.0)	$ 0.0	0.0	0.0	(133.0)
Common stock issued for:
Stock options exercised (in shares)	1.7	1.7
Stock options exercised	$ 32.4	$ 1.7	30.7	0.0	0.0
Other transactions (in shares)		0.0
Other transactions	(0.9)	$ 0.0	(0.9)	0.0	0.0
Stock-based compensation	7.3	$ 0.0	7.3	0.0	0.0
Balance (in shares) at Dec. 31, 2017		167.1
Balance at Dec. 31, 2017	$ 2,753.7	$ 167.1	$ 2,280.9	$ (484.6)	$ 790.3