General - Stock Compensation - Nonvested - Activity (Details)	6 Months Ended
	Jun. 30, 2019 $ / shares shares
Restricted stock awards
Shares
Outstanding, beginning of period (in shares) | shares	11,795
Awarded (in shares) | shares	20,152
Vested (in shares) | shares	(13,939)
Outstanding, end of period (in shares) | shares	18,008
Weighted Average Grant Date Fair Value
Outstanding, beginning of period (in dollars per share) | $ / shares	$ 89.05
Awarded (in dollars per share) | $ / shares	66.93
Vested (in dollars per share) | $ / shares	85.99
Outstanding, end of period (in dollars per share) | $ / shares	$ 66.66
Restricted Stock Units (RSUs)
Shares
Outstanding, beginning of period (in shares) | shares	156,750
Awarded (in shares) | shares	186,325
Vested (in shares) | shares	(68,993)
Forfeited (in shares) | shares	(14,288)
Outstanding, end of period (in shares) | shares	259,794
Weighted Average Grant Date Fair Value
Outstanding, beginning of period (in dollars per share) | $ / shares	$ 86.68
Awarded (in dollars per share) | $ / shares	66.57
Vested (in dollars per share) | $ / shares	81.95
Forfeited (in dollars per share) | $ / shares	82.76
Outstanding, end of period (in dollars per share) | $ / shares	$ 73.73
Performance Based Restricted Stock Units ("PSUs")
Shares
Outstanding, beginning of period (in shares) | shares	209,019
Awarded (in shares) | shares	83,087
Vested (in shares) | shares	(43,109)
Forfeited (in shares) | shares	(12,157)
Outstanding, end of period (in shares) | shares	236,840
Weighted Average Grant Date Fair Value
Outstanding, beginning of period (in dollars per share) | $ / shares	$ 103.38
Awarded (in dollars per share) | $ / shares	100.31
Vested (in dollars per share) | $ / shares	97.12
Forfeited (in dollars per share) | $ / shares	97.12
Outstanding, end of period (in dollars per share) | $ / shares	$ 103.76