Stock Compensation Plans (Details 2) $ / shares in Units, $ in Millions	9 Months Ended
	Sep. 30, 2017 USD ($) $ / shares shares
Time-Based RSUs
Shares
Outstanding, beginning of period (in shares) | shares	1,218,714
Granted (in shares) | shares	370,514
Vested (in shares) | shares	(299,164)
Forfeited (in shares) | shares	(131,472)
Outstanding, end of period (in shares) | shares	1,158,592
Weighted Average Grant-Date Fair Value
Outstanding, beginning of period (in dollars per share) | $ / shares	$ 35.92
Granted (in dollars per share) | $ / shares	54.71
Vested (in dollars per share) | $ / shares	36.68
Forfeited (in dollars per share) | $ / shares	40.05
Outstanding, end of period (in dollars per share) | $ / shares	$ 41.26
Total unrecognized compensation cost | $	$ 28.2
Weighted average period to recognize unrecognized compensation cost	2 years
Performance-Based RSUs
Shares
Outstanding, beginning of period (in shares) | shares	410,746
Granted (in shares) | shares	131,597
Vested (in shares) | shares	(118,044)
Forfeited (in shares) | shares	0
Outstanding, end of period (in shares) | shares	424,299
Weighted Average Grant-Date Fair Value
Outstanding, beginning of period (in dollars per share) | $ / shares	$ 35.27
Granted (in dollars per share) | $ / shares	56.59
Vested (in dollars per share) | $ / shares	36.85
Forfeited (in dollars per share) | $ / shares	0.00
Outstanding, end of period (in dollars per share) | $ / shares	$ 41.44
Total unrecognized compensation cost | $	$ 15.3
Weighted average period to recognize unrecognized compensation cost	2 years 7 days