Capital Stock - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions															1 Months Ended					3 Months Ended		12 Months Ended
	Dec. 11, 2015	Sep. 04, 2015	Jun. 10, 2015	Apr. 01, 2015	Dec. 09, 2014	Dec. 01, 2014	Nov. 25, 2014	Oct. 09, 2014	Sep. 10, 2014	Jul. 14, 2014	Jun. 25, 2014	Jun. 11, 2014	Mar. 27, 2014	Sep. 09, 2013	May. 31, 2015	Feb. 28, 2015	May. 31, 2014	May. 31, 2012	May. 31, 2011	Dec. 31, 2015	Mar. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Capital Unit [Line Items]
Early settlement of Purchase Contracts holder																				85,121		85,121
Tangible equity unit, common stock delivered on settlement																						43.0918
Cash dividends declared and paid per common share	$ 0.12	$ 0.12	$ 0.12	$ 0.12	$ 0.12				$ 0.12			$ 0.12	$ 0.12	$ 0.12								$ 0.48	$ 0.48	$ 0.24
Cash dividend per share to be paid																$ 0.12
Cash dividends payable date	Dec. 11, 2015	Sep. 04, 2015	Jun. 10, 2015	Apr. 01, 2015	Dec. 09, 2014				Sep. 10, 2014			Jun. 11, 2014	Mar. 27, 2014	Sep. 09, 2013								Apr. 01, 2016
Cash dividends payable date of record																						Mar. 10, 2016
Installment payment on unit payable date to be paid day month and year																				Dec. 01, 2015	Mar. 02, 2015
Installment payment on unit, quarterly installment payment																				$ 18.75	$ 18.75
Installment payment on unit, one-time incremental payment																					$ 1.25
Installment payment on unit, total installment payment																						$ 20.00
Number of additional shares authorized for issuance under incentive compensation plans																	2,700,000		3,000,000
Number of common stocks authorized for grant to directors, officers and other key employees																				8,000,000		8,000,000
Shares of common stock available for future grants																				3,262,892		3,262,892	3,000,183	1,033,186
Number of stock option grants in period																						0	0	0
Employee Stock Option
Capital Unit [Line Items]
Unearned compensation related to non-vested share awards																				$ 0.2		$ 0.2
Compensation expenses																						0.4	$ 0.0	$ 0.0
Compensation expenses, net of income taxes																						0.3
Intrinsic value of stock options exercised																						0.3	2.4	0.4
Proceeds from stock option exercises																						0.5	6.2	0.5
Service Based Restricted Shares
Capital Unit [Line Items]
Unearned compensation related to non-vested share awards																				10.4		10.4
Compensation expenses																						13.6	13.0	9.6
Compensation expenses, net of income taxes																						$ 8.2	7.9	5.8
Unearned compensation related to non-vested share awards, period of recognition																						2 years
Fair value of restricted shares vested																						$ 22.7	15.0	6.6
Performance Based Restricted Shares
Capital Unit [Line Items]
Compensation expenses																						5.8	3.7	1.6
Compensation expenses, net of income taxes																						$ 3.5	$ 2.2	$ 1.0
Vesting period																						3 years
Service Based Restricted Stock Units
Capital Unit [Line Items]
Unearned compensation related to non-vested share awards																				1.5		$ 1.5
Compensation expenses																						0.8
Compensation expenses, net of income taxes																						$ 0.5
Unearned compensation related to non-vested share awards, period of recognition																						2 years
Minimum
Capital Unit [Line Items]
Stock options, period to exercise, beginning																						1 year
Stock options, period to exercise, ending																						7 years
Maximum
Capital Unit [Line Items]
Stock options, period to exercise, beginning																						4 years
Stock options, period to exercise, ending																						10 years
Maximum | Employee Stock Option
Capital Unit [Line Items]
Intrinsic value of stock options outstanding																				$ 0.1		$ 0.1
Common Stock
Capital Unit [Line Items]
Equity offerings, net of costs (in shares)																						3,700,000	15,119,000
Common Stock Offerings
Capital Unit [Line Items]
Equity offerings, net of costs (in shares)							5,000,000			723,468	9,000,000
Option to purchase additional shares						395,759	750,000				1,350,000
Equity offering, net of offering costs							$ 101.0				$ 220.4
Period to purchase additional shares							30 days				30 days
Units Offering
Capital Unit [Line Items]
Period to purchase additional shares							13 days
Net proceeds from units offering net of underwriting discount and estimated offering expenses							$ 166.3
Units Offering | Tangible Equity Units
Capital Unit [Line Items]
Equity offerings, net of costs (in shares)							150,000
Option to purchase additional shares						22,500
Units Offering | Mandatorily Redeemable Preferred Stock
Capital Unit [Line Items]
Preferred stock, initial liquidation preference per share							$ 201.58
Gentiva Health Services Inc
Capital Unit [Line Items]
Shares of common stock part of Stock Consideration								9,700,000
Equity offerings, net of costs (in shares)																						15,000,000
Number of stock option grants in period																						1,075,965
Non Employee Director
Capital Unit [Line Items]
Number of additional shares authorized for issuance under incentive compensation plans															200,000			200,000
Gentiva Merger
Capital Unit [Line Items]
Number of additional shares authorized for issuance under incentive compensation plans																1,400,000