Consolidated Statements of Stockholders' Equity - USD ($) $ in Millions	Total	Cumulative Effect, Period of Adoption, Adjusted Balance	Cumulative Effect, Period of Adoption, Adjustment	Common Stock	Common Stock Cumulative Effect, Period of Adoption, Adjusted Balance	Common Stock Cumulative Effect, Period of Adoption, Adjustment	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Adjusted Balance	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment	Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss) Cumulative Effect, Period of Adoption, Adjusted Balance	Accumulated Other Comprehensive Income (Loss) Cumulative Effect, Period of Adoption, Adjustment
Stockholders' Equity Attributable to Parent	$ 1,986.6			$ 945.0			$ 1,052.6			$ (11.0)
Net income	202.2			0.0			202.2			0.0
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	$ (466.1)			0.0			0.0			(466.1)
Stock Repurchased and Retired During Period, Shares	5,040,896
Common shares purchased and retired	$ (199.0)			(199.0)			0.0			0.0
Stock issued during period, new issues (in shares)	46,913,370
Stock issued during period, RSU (in shares)	458,177
Stock Issued During Period, Value, New Issues	$ 1,722.5			1,722.5			0.0			0.0
Non-vested common shares forfeited or canceled	0.0			0.0			0.0			0.0
Stock compensation expense	0.1			0.1			0.0			0.0
Stock compensation expense	9.6			9.6			0.0			0.0
APIC, Share-based Payment Arrangement, Option, Increase for Cost Recognition	$ (182.1)			0.0			(182.1)			0.0
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested Options Forfeited, Number of Shares	106,891
Dividends declared (in usd per share)	$ 1.70
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period	17,807
Shares tendered in payment of option price and income tax withholding amounts, shares	4,877
Stockholders' Equity Attributable to Parent	$ 3,073.8			2,478.2			1,072.7			(477.1)
Common Stock, Value, Issued	0.0			0.0			0.0			0.0
Net income	257.5			0.0			257.5			0.0
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	$ 120.6			0.0			0.0			120.6
Stock Repurchased and Retired During Period, Shares	1,056,191
Common shares purchased and retired	$ (34.0)			(34.0)			0.0			0.0
Stock issued during period, RSU (in shares)	683,574
Non-vested common shares forfeited or canceled	$ 0.0			0.0			0.0			0.0
Stock compensation expense	4.7			4.7			0.0			0.0
APIC, Share-based Payment Arrangement, Option, Increase for Cost Recognition	$ (195.1)			0.0			(195.1)			0.0
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested Options Forfeited, Number of Shares	127,780
Dividends declared (in usd per share)	$ 1.88
Stockholders' Equity Attributable to Parent	$ 3,227.5	$ 3,228.7	$ 1.2	2,448.9	$ 2,448.9	$ 0.0	1,135.1	$ 1,136.3	$ 1.2	(356.5)	$ (356.5)	$ 0.0
Common Stock, Value, Issued	0.0			0.0			0.0			0.0
Net income	226.0			0.0			226.0			0.0
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	$ 34.6			0.0			0.0			34.6
Stock Repurchased and Retired During Period, Shares	49,568
Common shares purchased and retired	$ (1.2)			(1.2)			0.0			0.0
Stock issued during period, RSU (in shares)	807,913
Non-vested common shares forfeited or canceled	$ 0.0			0.0			0.0			0.0
Stock compensation expense	11.8			11.8			0.0			0.0
APIC, Share-based Payment Arrangement, Option, Increase for Cost Recognition	$ (195.9)			0.0			(195.9)			0.0
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested Options Forfeited, Number of Shares	114,007
Dividends declared (in usd per share)	$ 1.88
Stockholders' Equity Attributable to Parent	$ 3,304.0			2,459.5			1,166.4			(321.9)
Common Stock, Value, Issued	$ 0.0			$ 0.0			$ 0.0			$ 0.0