Condensed 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, 2016		165.4
Balance at Dec. 31, 2016	$ 2,273.0	$ 165.4	$ 2,243.8	$ (510.0)	$ 373.8
Net income (loss)	7.5	0.0	0.0	0.0	7.5
Other comprehensive income	24.6	0.0	0.0	24.6	0.0
Dividends paid:
Common stock ($0.40 per share)	$ (66.3)	$ 0.0	0.0	0.0	(66.3)
Common stock issued for:
Stock options exercised (in shares)	0.9	0.9
Stock options exercised	$ 15.8	$ 0.9	14.9	0.0	0.0
Other Transactions (in shares)		0.0
Other Transactions	0.6	$ 0.0	0.6	0.0	0.0
Stock-based compensation	3.4	$ 0.0	3.4	0.0	0.0
Balance (in shares) at Jun. 30, 2017		166.3
Balance at Jun. 30, 2017	2,258.6	$ 166.3	2,262.7	(485.4)	315.0
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
Income tax reclassification adjustment	0.0	0.0	0.0	(85.9)	85.9
Net income (loss)	79.5	0.0	0.0	0.0	79.5
Other comprehensive income	(2.7)	0.0	0.0	(2.7)	0.0
Dividends paid:
Common stock ($0.40 per share)	(66.9)	$ 0.0	0.0	0.0	(66.9)
Common stock repurchased and retired (in shares)		(0.3)
Common stock repurchased and retired	$ (9.1)	$ (0.3)	(8.8)	0.0	0.0
Common stock issued for:
Stock options exercised (in shares)	0.2	0.2
Stock options exercised	$ 2.2	$ 0.2	2.0	0.0	0.0
Other Transactions (in shares)		0.0
Other Transactions	0.6	$ 0.0	0.6	0.0	0.0
Stock-based compensation	5.8	$ 0.0	5.8	0.0	0.0
Balance (in shares) at Jun. 30, 2018		167.0
Balance at Jun. 30, 2018	$ 2,763.1	$ 167.0	$ 2,280.5	$ (573.2)	$ 888.8