Stock Option Summary (Details) - Employee Stock Option [Member] - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	6 Months Ended		12 Months Ended
	Jun. 30, 2019	Jun. 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 9 months 18 days	6 years 8 months 12 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)		101
Granted, weighted average exercise price (in dollars per share)		$ 69.30
Granted, weighted average grant date fair value		$ 24.83
Exercised (in shares)	(59)	(87)
Exercised, weighted average exercise price (in dollars per share)	$ 40.57	$ 40.08
Exercised, aggregate intrinsic value	$ 1,057	$ 2,779
Forfeited (in share)	(8)	(3)
Forfeited, weighted average grant date fair value (in dollars per share)	$ 67.38	$ 68.43
Expired (in shares)	(9)	(66)
Expired, weighted average exercise price (in dollars per share)	$ 66.36	$ 95.33
Outstanding, ending balance (in shares)	819	943	895	956
Outstanding, ending balance, weighted average exercise price per share (in dollars per share)	$ 48.06	$ 46.92	$ 47.93	$ 47.10
Outstanding, weighted average remaining contractual life	5 years 9 months 18 days	6 years 8 months 12 days	6 years 2 months 12 days	6 years 3 months 18 days
Outstanding, ending balance, aggregate intrinsic value	$ 12,958	$ 14,066	$ 4,806	$ 21,965
Exercisable (in shares)	691
Exercisable, weighted average exercise price (in dollars per share)	$ 44.67
Exercisable, weighted average remaining contractual term	5 years 3 months 18 days
Exercisable, aggregate intrinsic value	$ 12,841
Expected to Vest [Member]
[Line Items]
Outstanding, weighted average remaining contractual life	8 years 4 months 24 days
Outstanding, ending balance (in shares)	128
Outstanding, ending balance, weighted average exercise price per share (in dollars per share)	$ 66.35
Outstanding, weighted average remaining contractual life	8 years 4 months 24 days
Outstanding, ending balance, aggregate intrinsic value	$ 117