Share-Based Compensation - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($) plan shares	Dec. 31, 2014 USD ($) shares	Dec. 31, 2013 USD ($) shares
Share-Based Compensation (Textual) [Abstract]
Number of stock incentive plans | plan	2
Number of shares available for issuance remaining | shares	3,120,750
Stock option granted (shares) | shares	0	0	0
Aggregate intrinsic value of stock options exercised	$ 6.4	$ 4.6	$ 11.4
Tax benefit from stock option exercised	2.5	1.8	4.5
Fair value of options vested during period	$ 1.8	1.8	1.8
Shares of non-vested common stock granted | shares	130,900
Board Of Directors [Member]
Share-Based Compensation (Textual) [Abstract]
Minimum vesting period of outstanding options and non vested shares (years)	3 years
Shares of non-vested common stock granted | shares	5,892
Employees Non Vested Shares One [Member]
Share-Based Compensation (Textual) [Abstract]
Shares of non-vested common stock granted | shares	125,008
Employees - Non Vested Shares Two Member
Share-Based Compensation (Textual) [Abstract]
Minimum vesting period of outstanding options and non vested shares (years)	4 years
Employee Stock Option [Member]
Share-Based Compensation (Textual) [Abstract]
Total unrecognized compensation cost related to stock options	$ 0.4
Weighted-average period of recognition of unrecognized compensation cost	7 months 20 days
Compensation cost charged against income	$ 1.3	1.6	1.8
Income tax benefit recognized during the period	$ 0.5	0.6	0.7
Nonvested Stock Awards [Member]
Share-Based Compensation (Textual) [Abstract]
Weighted-average period of recognition of unrecognized compensation cost	2 years 11 months 21 days
Compensation cost charged against income	$ 6.0	7.5	8.8
Income tax benefit recognized during the period	$ 2.3	$ 2.9	3.4
Shares of non-vested common stock granted | shares	131,000	172,000
Total unrecognized compensation cost related to stock options	$ 15.1
Nonvested Stock Awards [Member] | Board Of Directors [Member]
Share-Based Compensation (Textual) [Abstract]
Minimum vesting period of outstanding options and non vested shares (years)	3 years
Restricted Stock Units (RSUs) [Member]
Share-Based Compensation (Textual) [Abstract]
Weighted-average period of recognition of unrecognized compensation cost	3 years 2 months 28 days
Compensation cost charged against income	$ 9.0	$ 8.1	3.5
Income tax benefit recognized during the period	3.5	$ 3.2	$ 1.4
Unrecognized compensation cost	$ 14.6
Number of restricted stock units granted | shares	249,665	253,000
Annual award vesting rights, percentage	25.00%
Restricted Stock Units (RSUs) [Member] | Executive Officer [Member]
Share-Based Compensation (Textual) [Abstract]
Minimum vesting period of outstanding options and non vested shares (years)	4 years
Number of shares authorized by right | shares	1
Award performance period	3 years
Minimum [Member]
Share-Based Compensation (Textual) [Abstract]
Minimum vesting period of outstanding options and non vested shares (years)	3 years
Expiration period of outstanding options (years)	5 years
Maximum [Member]
Share-Based Compensation (Textual) [Abstract]
Minimum vesting period of outstanding options and non vested shares (years)	6 years
Expiration period of outstanding options (years)	10 years
Anniversary One | Minimum [Member] | Nonvested Stock Awards [Member]
Share-Based Compensation (Textual) [Abstract]
Vesting rights, percentage	33.33%
Anniversary One | Maximum [Member] | Nonvested Stock Awards [Member]
Share-Based Compensation (Textual) [Abstract]
Vesting rights, percentage	25.00%
Anniversary Two | Minimum [Member] | Nonvested Stock Awards [Member]
Share-Based Compensation (Textual) [Abstract]
Vesting rights, percentage	33.33%
Anniversary Two | Maximum [Member] | Nonvested Stock Awards [Member]
Share-Based Compensation (Textual) [Abstract]
Vesting rights, percentage	25.00%
Anniversary Three | Minimum [Member] | Nonvested Stock Awards [Member]
Share-Based Compensation (Textual) [Abstract]
Vesting rights, percentage	33.33%
Anniversary Three | Maximum [Member] | Nonvested Stock Awards [Member]
Share-Based Compensation (Textual) [Abstract]
Vesting rights, percentage	25.00%
Anniversary Four | Maximum [Member] | Nonvested Stock Awards [Member]
Share-Based Compensation (Textual) [Abstract]
Vesting rights, percentage	25.00%