Stock Based Compensation Plan (Details) (USD $) | 6 Months Ended |
In Millions, except Share data, unless otherwise specified | Jun. 30, 2014 | Jun. 30, 2013 |
Weighted-Average Award Price [Roll Forward] | ' | ' |
Period of restrictions over awards | '4 years | ' |
Compensation expense | $1.80 | $2 |
Total compensation cost related to unvested equity awards | 6.1 | ' |
Weighted-average period of recognition of cost | '2 years 6 months | ' |
Restricted Stock Award [Member] | ' | ' |
Shares or Units and Rights [Roll Forward] | ' | ' |
Outstanding, beginning balance (in shares) | 437,000 | ' |
Granted (in shares) | 146,248 | ' |
Restrictions lapsed or exercised (in shares) | -235,925 | ' |
Forfeited (in shares) | -16,060 | ' |
Outstanding, ending balance (in shares) | 331,263 | ' |
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) | $28.73 | ' |
Restrictions lapsed or exercised (in dollars per share) | $14.01 | ' |
Forfeited (in dollars per share) | $21.25 | ' |
Outstanding, ending balance (in dollars per share) | $20.75 | ' |
Exercisable, ending balance (in dollars per share) | $0 | ' |
Vesting period | '3 years | ' |
Aggregate intrinsic value of outstanding awards | 8.3 | ' |
Stock-Settled Appreciation Rights [Member] | ' | ' |
Shares or Units and Rights [Roll Forward] | ' | ' |
Outstanding, beginning balance (in shares) | 149,700 | ' |
Granted (in shares) | 0 | ' |
Restrictions lapsed or exercised (in shares) | -11,875 | ' |
Forfeited (in shares) | -6,000 | ' |
Outstanding, ending balance (in shares) | 131,825 | ' |
Exercisable, ending balance (in shares) | 53,825 | ' |
Weighted-Average Award Price [Roll Forward] | ' | ' |
Outstanding, beginning balance (in dollars per share) | $15.78 | ' |
Granted (in dollars per share) | $0 | ' |
Restrictions lapsed or exercised (in dollars per share) | $12.80 | ' |
Forfeited (in dollars per share) | $18.14 | ' |
Outstanding, ending balance (in dollars per share) | $15.94 | ' |
Exercisable, ending balance (in dollars per share) | $12.75 | ' |
Aggregate intrinsic value of outstanding awards | 1.2 | ' |
Aggregate intrinsic value of vested awards | $0.70 | ' |
Performance Shares [Member] | ' | ' |
Shares or Units and Rights [Roll Forward] | ' | ' |
Granted (in shares) | 39,890 | ' |