Goodwill and Other Intangible Assets - Change in Goodwill (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Goodwill [Roll Forward]
Balance at the beginning of the period	$ 119,029	$ 119,029	$ 119,029
Additions as a result of acquisitions	121,910	0	0
Balance at the end of the period	$ 240,939	$ 119,029	$ 119,029