Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Millions	Total	Common stock [Member]	Treasury Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of period, Shares			(19,100,000)
Balance at beginning of year at Dec. 31, 2012		66,000,000
Balance at beginning of period, Common Stock at Dec. 31, 2012		$ 41.2
Balance at beginning of period at Dec. 31, 2012			$ (560.3)	$ 658.5	$ 1,249.4	$ (144.6)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock, Shares		300,000
Issuance of common stock		$ 0.1		1.1
Stock repurchases, Shares	1,400,000
Stock repurchases	$ (68.6)
Share-based compensation effects				9.3
Net income	169.3				169.3
Dividends declared					(60.3)
Other comprehensive income (loss)	101.9
Balance at end of period, Common Stock, Shares at Dec. 31, 2013		66,300,000
Balance at end of period, Common Stock at Dec. 31, 2013		$ 41.3
Balance at end of period at Dec. 31, 2013	$ 1,397.0		$ (628.9)	668.9	1,358.4	(42.7)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of period, Shares			(20,500,000)
Issuance of common stock, Shares		300,000
Issuance of common stock		$ 0.1		0.0
Stock repurchases, Shares	1,900,000
Stock repurchases	$ (124.6)
Share-based compensation effects				3.9
Net income	205.0				205.0
Dividends declared					(61.7)
Other comprehensive income (loss)	$ (105.7)					(105.7)
Balance at end of period, Common Stock, Shares at Dec. 31, 2014	66,600,984	66,600,000
Balance at end of period, Common Stock at Dec. 31, 2014	$ 41.4	$ 41.4
Balance at end of period at Dec. 31, 2014	$ 1,314.0		$ (753.5)	672.8	1,501.7	(148.4)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of period, Shares			(22,400,000)
Issuance of common stock, Shares		200,000
Issuance of common stock		$ 0.1		0.0
Stock repurchases, Shares	2,400,000
Stock repurchases	$ (125.4)
Share-based compensation effects				4.6
Net income	205.3
Dividends declared					(68.0)
Other comprehensive income (loss)	$ (50.4)
Balance at end of period, Common Stock, Shares at Dec. 31, 2015	66,776,290.000000	66,800,000
Balance at end of period, Common Stock at Dec. 31, 2015	$ 41.5	$ 41.5
Balance at end of period at Dec. 31, 2015	$ 1,280.2		$ (878.9)	$ 677.4	$ 1,639.0	$ (198.8)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of period, Shares			(24,800,000)