Stock Option Summary (Details) - Share-based Payment Arrangement, Option [Member] - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
[Line Items]
Outstanding, beginning balance (in shares)	895	956	956
Outstanding, beginning balance, weighted average exercise price per share (in dollars per share)	$ 47.93	$ 47.10	$ 47.10
Outstanding, weighted average remaining contractual life	5 years 6 months	6 years 7 months 6 days	6 years 2 months 12 days	6 years 3 months 18 days
Outstanding, beginning balance, aggregate intrinsic value	$ 4,806	$ 21,965	$ 21,965
Shares converted upon acquisition (in shares)		42
Shares converted upon acquisition, weighted average exercise price (in dollars per share)		$ 51.86
Shares converted upon acquisition, weighted average grant date fair value		$ 14.86
Granted (in shares)	76	117
Granted, weighted average exercise price (in dollars per share)	$ 76.55	$ 68.90
Granted, weighted average grant date fair value	$ 26.20	$ 24.55
Exercised (in shares)	(117)	(151)
Exercised, weighted average exercise price (in dollars per share)	$ 40.10	$ 38.98
Exercised, aggregate intrinsic value	$ 2,745	$ 4,509
Forfeited (in share)	(8)	(3)
Forfeited, weighted average grant date fair value (in dollars per share)	$ 67.38	$ 68.43
Expired (in shares)	(11)	(66)
Expired, weighted average exercise price (in dollars per share)	$ 66.24	$ 95.31
Outstanding, ending balance (in shares)	835	895	895	956
Outstanding, ending balance, weighted average exercise price per share (in dollars per share)	$ 51.22	$ 47.92	$ 47.93	$ 47.10
Outstanding, weighted average remaining contractual life	5 years 6 months	6 years 7 months 6 days	6 years 2 months 12 days	6 years 3 months 18 days
Outstanding, ending balance, aggregate intrinsic value	$ 19,190	$ 15,332	$ 4,806	$ 21,965
Exercisable (in shares)	640
Exercisable, weighted average exercise price (in dollars per share)	$ 45.32
Exercisable, weighted average remaining contractual term	4 years 6 months
Exercisable, aggregate intrinsic value	$ 18,328
Expected to Vest [Member]
[Line Items]
Outstanding, weighted average remaining contractual life	8 years 9 months 18 days
Outstanding, ending balance (in shares)	195
Outstanding, ending balance, weighted average exercise price per share (in dollars per share)	$ 70.56
Outstanding, weighted average remaining contractual life	8 years 9 months 18 days
Outstanding, ending balance, aggregate intrinsic value	$ 861