Stock Based Compensation Plans (Details) (USD $) | 9 Months Ended |
In Millions, except Share data, unless otherwise specified | Sep. 30, 2013 | Sep. 30, 2012 |
| Plan |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ' | ' |
Number of compensation plans | 2 | ' |
Shares [Roll Forward] | ' | ' |
Outstanding, beginning balance (in shares) | 50,000 | ' |
Granted (in shares) | 0 | ' |
Exercised or restrictions lapsed (in shares) | -48,000 | ' |
Forfeited or expired (options) (in shares) | -2,000 | ' |
Weighted-Average Exercise Price [Roll Forward] | ' | ' |
Outstanding, beginning balance (in dollars per share) | $20.56 | ' |
Granted (in dollars per share) | $0 | ' |
Exercised or restrictions lapsed (in dollars per share) | $20.75 | ' |
Forfeited or expired (options) (in dollars per share) | $15.90 | ' |
Period of restrictions over awards | '4 years | ' |
Compensation expense | $2.70 | $1.90 |
Total compensation cost related to unvested equity awards | 5.1 | ' |
Weighted-average period of recognition of cost | '2 years 8 months 12 days | ' |
Restricted Stock Award [Member] | ' | ' |
Shares or Units and Rights [Roll Forward] | ' | ' |
Outstanding, beginning balance (in shares) | 555,925 | ' |
Granted (in shares) | 162,150 | ' |
Exercised or restrictions lapsed (in shares) | -277,975 | ' |
Forfeited or expired (options) (in shares) | -2,350 | ' |
Outstanding, ending balance (in shares) | 437,750 | ' |
Exercisable, ending balance (in shares) | 0 | ' |
Weighted-Average Award Price [Roll Forward] | ' | ' |
Outstanding, beginning balance (in dollars per share) | $12.28 | ' |
Granted (in dollars per share) | $18.15 | ' |
Exercised or restrictions lapsed (in dollars per share) | $12.24 | ' |
Forfeited or expired (options) (in dollars per share) | $14.56 | ' |
Outstanding, ending balance (in dollars per share) | $14.46 | ' |
Exercisable, ending balance (in dollars per share) | $0 | ' |
Weighted-Average Exercise Price [Roll Forward] | ' | ' |
Aggregate intrinsic value of outstanding awards | 10.7 | ' |
Stock-Settled Appreciation Rights [Member] | ' | ' |
Shares or Units and Rights [Roll Forward] | ' | ' |
Outstanding, beginning balance (in shares) | 121,749 | ' |
Granted (in shares) | 112,000 | ' |
Exercised or restrictions lapsed (in shares) | -80,049 | ' |
Forfeited or expired (options) (in shares) | 0 | ' |
Outstanding, ending balance (in shares) | 153,700 | ' |
Exercisable, ending balance (in shares) | 41,700 | ' |
Weighted-Average Award Price [Roll Forward] | ' | ' |
Outstanding, beginning balance (in dollars per share) | $8.85 | ' |
Granted (in dollars per share) | $18.14 | ' |
Exercised or restrictions lapsed (in dollars per share) | $8.92 | ' |
Forfeited or expired (options) (in dollars per share) | $0 | ' |
Outstanding, ending balance (in dollars per share) | $15.58 | ' |
Exercisable, ending balance (in dollars per share) | $8.72 | ' |
Weighted-Average Exercise Price [Roll Forward] | ' | ' |
Aggregate intrinsic value of outstanding awards | 1.4 | ' |
Aggregate intrinsic value of vested awards | $0.70 | ' |