Stock Compensation Plans (Details 2) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2017 USD ($) $ / shares shares
Time-Based RSUs
Shares
Outstanding at beginning of period (in shares) | shares	1,218,714
Granted (in shares) | shares	330,762
Vested (in shares) | shares	(279,549)
Forfeited (in shares) | shares	(61,193)
Outstanding at end of period (in shares) | shares	1,208,734
Weighted Average Grant-Date Fair Value
Outstanding at beginning of period (in dollars per share) | $ / shares	$ 35.92
Granted (in dollars per share) | $ / shares	54.49
Vested (in dollars per share) | $ / shares	36.84
Forfeited (in dollars per share) | $ / shares	39.25
Outstanding at end of period (in dollars per share) | $ / shares	$ 40.62
Total unrecognized compensation cost | $	$ 34.6
Weighted average period to recognize unrecognized compensation cost	2 years 3 months 19 days
Performance-Based RSUs
Shares
Outstanding at 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 at end of period (in shares) | shares	424,299
Weighted Average Grant-Date Fair Value
Outstanding at 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 at end of period (in dollars per share) | $ / shares	$ 41.44
Total unrecognized compensation cost | $	$ 20.2
Weighted average period to recognize unrecognized compensation cost	2 years 4 months 28 days