Summary of Significant Accounting Policies - Contract Assets and Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Contract Assets
Balance at beginning of period	$ 2,736	$ 10,213	$ 10,213
Change due to acquisitions / disposals	436		6,573
Change due to conditional versus unconditional	4,394		(14,050)
Change related to credit allowance	(25)
Balance at end of period	7,541		2,736
Contract Liabilities
Balance at beginning of period	166,918	130,986	130,986
Change due to acquisitions / disposals	12,851		31,556
Change in timing for performance obligation to be satisfied	35,337		4,376
Balance at end of period	215,106		$ 166,918
Revenue related to our contract liabilities	$ 126,800
Calculated under Revenue Guidance in Effect before Topic 606 [Member]
Contract Liabilities
Revenue related to our contract liabilities		$ 105,600