Earnings (Loss) Per Share and Shareholder’s Equity (Narrative) (Details) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Mar. 31, 2016 $ / shares	Dec. 31, 2015 USD ($) $ / shares shares	Sep. 30, 2015 $ / shares	Jun. 30, 2015 $ / shares	Mar. 31, 2015 $ / shares	Dec. 31, 2014 $ / shares	Sep. 30, 2014 $ / shares	Jun. 30, 2014 $ / shares	Dec. 31, 2015 USD ($) $ / shares shares	Dec. 31, 2014 USD ($) $ / shares shares	Dec. 31, 2013 USD ($) $ / shares shares	Dec. 31, 2012 USD ($) $ / shares
Common Stock, Dividends, Per Share, Cash Paid | $ / shares	$ 0.08	$ 0.08	$ 0.08	$ 0.07	$ 0.07	$ 0.07	$ 0.07	$ 0.06
Repurchase of shares									3,100,000	2,300,000	6,700,000
Repurchase of Common Shares | $									$ 72.5	$ 46.3	$ 119.0
Stock repurchased but not settled in cash | $									$ 0.9
Repurchase of shares, average price per share | $ / shares									$ 23.30
Incremental Common Shares Attributable to Dilutive Effect of Conversion of Debt Securities									5,800,000	4,500,000	4,700,000
Stock Repurchase Program, Remaining Authorized Repurchase Amount | $		$ 250.0							$ 250.0
Stock Repurchase Program, Authorized Amount | $		$ 214.7							$ 214.7
Preferred Stock, With Voting Rights		4,000,000							4,000,000
Common Stock, Dividends, Per Share, Declared | $ / shares	$ 0.08								$ 0.31	$ 0.27	$ 0.24
Preferred Stock, Non-voting		1,000,000							1,000,000
Preferred Stock, Shares Issued		0							0
Restricted Stock Units (RSUs) [Member]
Antidilutive securities excluded from diluted EPS									400,000
5.75% Junior Subordinated Convertible Debentures [Member]
Debt Instrument, Face Amount | $												$ 125.0
Interest rate on unsecured senior notes												5.75%
Debt Instrument, Maturity Date												Sep. 15, 2029
Junior subordinated convertible debentures convertible conversion price | $ / shares		$ 11.50							$ 11.50			$ 12.07
Junior subordinated convertible debentures convertible equity instruments in conversion									86.95			82.82
Debt Instrument, Convertible, Terms of Conversion Feature									1000			1000
2014 Performance grants [Domain] | Restricted Stock Units (RSUs) [Member]
Antidilutive securities excluded from diluted EPS									300,000