Stock Based Compensation Plan (Details) - USD ($) $ / shares in Units, $ in Millions | 3 Months Ended |
Mar. 31, 2017 | Mar. 31, 2016 |
Additional Disclosures [Abstract] | | |
Vesting period of awards | 4 years | |
Compensation expense | $ 1.3 | $ 1 |
Total compensation cost related to unvested equity awards | $ 6.9 | |
Weighted-average period of recognition of cost | 2 years 7 months 6 days | |
Restricted Stock Award [Member] | | |
Shares or Units and Rights [Roll Forward] | | |
Outstanding, beginning balance (in shares) | 397,320 | |
Granted (in shares) | 188,290 | |
Restrictions lapsed or exercised (in shares) | (23,847) | |
Forfeited (in shares) | 0 | |
Outstanding, ending balance (in shares) | 561,763 | |
Exercisable, ending balance (in shares) | 0 | |
Restricted units expected to vest (in shares) | 561,763 | |
Weighted-Average Award Price [Roll Forward] | | |
Outstanding, beginning balance (in dollars per share) | $ 21.64 | |
Granted (in dollars per share) | 21.80 | |
Restrictions lapsed or exercised (in dollars per share) | 28.93 | |
Forfeited (in dollars per share) | 0 | |
Outstanding, ending balance (in dollars per share) | 21.39 | |
Exercisable, ending balance (in dollars per share) | 0 | |
Restricted units expected to vest (in dollars per share) | $ 21.39 | |
Additional Disclosures [Abstract] | | |
Vesting period of awards | 3 years | |
Aggregate intrinsic value of outstanding awards | $ 13.7 | |
Stock-Settled Appreciation Rights [Member] | | |
Shares or Units and Rights [Roll Forward] | | |
Outstanding, beginning balance (in shares) | 100,875 | |
Granted (in shares) | 0 | |
Restrictions lapsed or exercised (in shares) | 0 | |
Forfeited (in shares) | 0 | |
Outstanding, ending balance (in shares) | 100,875 | |
Exercisable, ending balance (in shares) | 74,875 | |
Restricted units expected to vest (in shares) | 0 | |
Weighted-Average Award Price [Roll Forward] | | |
Outstanding, beginning balance (in dollars per share) | $ 18.14 | |
Granted (in dollars per share) | 0 | |
Restrictions lapsed or exercised (in dollars per share) | 0 | |
Forfeited (in dollars per share) | 0 | |
Outstanding, ending balance (in dollars per share) | 18.14 | |
Exercisable, ending balance (in dollars per share) | 18.14 | |
Restricted units expected to vest (in dollars per share) | $ 0 | |
Additional Disclosures [Abstract] | | |
Aggregate intrinsic value of vested awards | $ 0.5 | |
Aggregate intrinsic value of outstanding awards | $ 0.6 | |
Performance Shares [Member] | | |
Shares or Units and Rights [Roll Forward] | | |
Granted (in shares) | 59,000 | |
Performance Shares [Member] | Maximum [Member] | | |
Additional Disclosures [Abstract] | | |
Vesting period of awards | 4 years | |
Performance Shares [Member] | Minimum [Member] | | |
Additional Disclosures [Abstract] | | |
Vesting period of awards | 1 year | |