Stock-Based Compensation (Narrative) (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended	12 Months Ended					12 Months Ended				12 Months Ended									12 Months Ended					12 Months Ended
	Mar. 31, 2013	Dec. 31, 2013	Dec. 31, 2013 Stock Appreciation Rights (SARs) [Member]	Dec. 31, 2012 Stock Appreciation Rights (SARs) [Member]	Dec. 31, 2011 Stock Appreciation Rights (SARs) [Member]	Dec. 31, 2010 Stock Appreciation Rights (SARs) [Member]	Dec. 31, 2013 Restricted Stock [Member]	Dec. 31, 2012 Restricted Stock [Member]	Dec. 31, 2011 Restricted Stock [Member]	Dec. 31, 2010 Restricted Stock [Member]	Dec. 31, 2013 Restricted Stock [Member] Minimum [Member]	Dec. 31, 2013 Restricted Stock [Member] Maximum [Member]	Dec. 31, 2013 Restricted Stock [Member] First Half of 2016 [Member]	Dec. 31, 2012 Restricted Stock [Member] First Half of 2015 [Member]	Dec. 31, 2011 Restricted Stock [Member] First Half of 2014 [Member]	Dec. 31, 2013 Stock Options [Member]	Dec. 31, 2012 Stock Options [Member]	Dec. 31, 2011 Stock Options [Member]	Dec. 31, 2010 Stock Options [Member]	Dec. 31, 2013 Directors Plan [Member]	Dec. 31, 2012 Directors Plan [Member]	Dec. 31, 2011 Directors Plan [Member]	Dec. 31, 2010 Directors Plan [Member]	Dec. 31, 2013 Incentive Stock Grants [Member]	Dec. 31, 2013 2011 [Member] Restricted Stock [Member]	Dec. 31, 2013 2012 [Member] Restricted Stock [Member]	Dec. 31, 2013 2013 [Member] Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost related to unvested awards		$ 14.2
Unrecognized compensation cost, expect to be capitalized		2.4
Weighted average years over which this cost will be recognized		0 years 9 months 18 days
Maximum number of shares of common stock allowed for the issuance		3,300,000																						2,000,000
Number of shares, granted			0	0	0		453,549	376,445	211,050
Expire years			10 years													10 years				10 years
Shares vested			0	0	33,745											0	0	0
Number of shares, ending balance			145,901	145,901	145,901	145,901	776,743	589,527	447,961	446,125
Aggregate intrinsic value			0.7				40.1													1.0
Weighted average remaining contractual term, years			3 years 7 months 6 days													1 year				4 years 7 months 6 days
Vesting Period											2 years	3 years								0 years 6 months
Percentage of restricted stock awards to be vested as performance shares to executives							30.00%
Restricted stock awards granted to designated executive officers													57,405	46,441	20,062
Performance evaluation period	3 years
Performance percentage criteria											0.00%	150.00%													65.25%	100.00%	100.00%
Grant date fair value							21.3	16.9	10.8													0.7
Number of Shares, Vested							(248,003)	(220,788)	(190,262)
Exercised intrinsic value							11.3									1.1
Restricted stock weighted average remaining contractual term, years							1 year
Maximum Number of Shares of Common Stock Previously Allowed for the Issuance																2,700,000
Vesting rate of options																20.00%
Cash received from the options exercised																0.1				0.6
Options Outstanding																68,920	118,030	138,980	184,765	171,500	192,500	199,500	178,500
Weighted average grant date price, ending balance			$ 46.59	$ 46.59	$ 46.59	$ 46.59	$ 48.70	$ 48.11	$ 47.44	$ 47.39						$ 37.81	$ 33.03	$ 31.39	$ 31.11	$ 51.70	$ 49.39	$ 48.37	$ 48.77
Exercisable options intrinsic value																$ 1.0				$ 0.2
Director option awards																					3,500
Options granted																0	0	0		0	0	31,500
Number of Shares, Exercised																(48,110)	(18,850)	(42,285)		(17,500)	(7,000)	(10,500)