Net (Loss) Income Per Share, Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 18, 2015	Jul. 01, 2015
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Options outstanding to purchase common shares		16,645	16,645
Average exercise price per share		$ 80.01	$ 80.01
Class of Warrant or Right, Exercise Price of Warrants or Rights					$ 60.20	$ 60.44
Payment of cash dividends to stockholders		$ 28.1	$ 25.4	$ 23.0
Payment of quarterly cash dividends		$ 1.60	$ 1.40	$ 1.20
Cash dividend returned to the Company	$ 0.6	$ 0.0	$ 0.0	$ 0.6
Shares returned from distribution of third-party trust, shares				9,001
Repurchase of common shares pursuant to an authorization from the Board, shares		647,520	633,230	0
Weighted-average price of repurchases of common shares		$ 76.35	$ 70.87
Repurchase of common shares pursuant to an authorization from the Board, value		$ 49.4	$ 44.9	$ 79.3
Common shares available for additional share repurchase		$ 123.3	$ 72.8
Common Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Stock Issued During Period, Shares, Other		1,015,185
Shares returned from distribution of third-party trust, shares	9,001
Repurchase of common shares pursuant to an authorization from the Board, shares		647,520	633,230	1,232,077
Convertible Notes | Convertible Notes Payable
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Stock Issued During Period, Shares, Other		1,015,185
Warrant Transactions
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Number of common shares underlying the Warrants outstanding			3,700,000