Stock Based Compensation Plan (Details) (USD $) | 3 Months Ended |
In Millions, except Share data, unless otherwise specified | Mar. 31, 2014 | Mar. 31, 2013 |
Weighted-Average Award Price [Roll Forward] | ' | ' |
Period of restrictions over awards | '4 years | ' |
Compensation expense | $0.90 | $0.80 |
Total compensation cost related to unvested equity awards | 7 | ' |
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) | 437,000 | ' |
Granted (in shares) | 138,565 | ' |
Forfeited (in shares) | -3,850 | ' |
Outstanding, ending balance (in shares) | 571,715 | ' |
Exercisable, ending balance (in shares) | 0 | ' |
Weighted-Average Award Price [Roll Forward] | ' | ' |
Outstanding, beginning balance (in dollars per share) | $14.46 | ' |
Granted (in dollars per share) | $28.92 | ' |
Forfeited (in dollars per share) | $20.80 | ' |
Outstanding, ending balance (in dollars per share) | $17.92 | ' |
Exercisable, ending balance (in dollars per share) | $0 | ' |
Vesting period | '3 years | ' |
Aggregate intrinsic value of outstanding awards | 17 | ' |
Stock-Settled Appreciation Rights [Member] | ' | ' |
Shares or Units and Rights [Roll Forward] | ' | ' |
Outstanding, beginning balance (in shares) | 149,700 | ' |
Granted (in shares) | 0 | ' |
Forfeited (in shares) | 0 | ' |
Outstanding, ending balance (in shares) | 149,700 | ' |
Exercisable, ending balance (in shares) | 37,700 | ' |
Weighted-Average Award Price [Roll Forward] | ' | ' |
Outstanding, beginning balance (in dollars per share) | $15.78 | ' |
Outstanding, ending balance (in dollars per share) | $15.78 | ' |
Exercisable, ending balance (in dollars per share) | $8.76 | ' |
Aggregate intrinsic value of outstanding awards | 2.1 | ' |
Aggregate intrinsic value of vested awards | $0.80 | ' |
Performance Shares [Member] | ' | ' |
Shares or Units and Rights [Roll Forward] | ' | ' |
Granted (in shares) | 39,890 | ' |