Stock Compensation - Summary of Stock Option Activity (Details)	9 Months Ended
	Sep. 30, 2018 $ / shares shares
Non-vested restricted stock
Shares
Beginning balance (in shares) | shares	405,536
Restricted stock units granted (in shares) | shares	133,920
Vested and paid (in shares) | shares	(148,041)
Forfeited (in shares) | shares	(2,716)
Ending balance (in shares) | shares	388,699
Weighted Average Price
Beginning balance (in dollars per share) | $ / shares	$ 44.58
Granted (in dollars per share) | $ / shares	52.21
Vested (in dollars per share) | $ / shares	56.83
Forfeited (in dollars per share) | $ / shares	49.15
Ending balance (in dollars per share) | $ / shares	$ 42.51
Performance share awards
Shares
Beginning balance (in shares) | shares	400,037
Restricted stock units granted (in shares) | shares	158,262
Vested and paid (in shares) | shares	(112,710)
Forfeited (in shares) | shares	(3,129)
Ending balance (in shares) | shares	442,460
Weighted Average Price
Beginning balance (in dollars per share) | $ / shares	$ 55.65
Granted (in dollars per share) | $ / shares	68.08
Vested (in dollars per share) | $ / shares	83.94
Forfeited (in dollars per share) | $ / shares	60.98
Ending balance (in dollars per share) | $ / shares	$ 52.85