Stock Based Compensation Plan (Details) - USD ($) $ / shares in Units, $ in Millions | 6 Months Ended |
Jun. 30, 2015 | Jun. 30, 2014 |
Weighted-Average Award Price [Roll Forward] | | |
Period of restrictions over awards | 4 years | |
Compensation expense | $ 2.2 | $ 1.8 |
Total compensation cost related to unvested equity awards | $ 6.5 | |
Weighted-average period of recognition of cost | 2 years 4 months 24 days | |
Restricted Stock Award [Member] | | |
Shares or Units and Rights [Roll Forward] | | |
Outstanding, beginning balance (in shares) | 321,322 | |
Granted (in shares) | 171,735 | |
Restrictions lapsed or exercised (in shares) | (147,595) | |
Forfeited (in shares) | (4,202) | |
Outstanding, ending balance (in shares) | 341,260 | |
Exercisable, ending balance (in shares) | 0 | |
Weighted-Average Award Price [Roll Forward] | | |
Outstanding, beginning balance (in dollars per share) | $ 20.49 | |
Granted (in dollars per share) | 24 | |
Restrictions lapsed or exercised (in dollars per share) | 18.94 | |
Forfeited (in dollars per share) | 25.08 | |
Outstanding, ending balance (in dollars per share) | 22.87 | |
Exercisable, ending balance (in dollars per share) | $ 0 | |
Vesting period | 3 years | |
Aggregate intrinsic value of outstanding awards | $ 7.4 | |
Stock-Settled Appreciation Rights [Member] | | |
Shares or Units and Rights [Roll Forward] | | |
Outstanding, beginning balance (in shares) | 129,975 | |
Granted (in shares) | 0 | |
Restrictions lapsed or exercised (in shares) | (19,100) | |
Forfeited (in shares) | 0 | |
Outstanding, ending balance (in shares) | 110,875 | |
Exercisable, ending balance (in shares) | 58,875 | |
Weighted-Average Award Price [Roll Forward] | | |
Outstanding, beginning balance (in dollars per share) | $ 16.04 | |
Granted (in dollars per share) | 0 | |
Restrictions lapsed or exercised (in dollars per share) | 8.74 | |
Forfeited (in dollars per share) | 0 | |
Outstanding, ending balance (in dollars per share) | 17.29 | |
Exercisable, ending balance (in dollars per share) | $ 16.54 | |
Aggregate intrinsic value of vested awards | $ 0.3 | |
Aggregate intrinsic value of outstanding awards | $ 0.5 | |
Performance Shares [Member] | | |
Shares or Units and Rights [Roll Forward] | | |
Granted (in shares) | 52,377 | |