Revenue from Contracts with Customers - Contract Assets and Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Contract Assets
Balance at beginning of period	$ 18,622	$ 2,736	$ 2,736
Change due to acquisitions / disposals	472		9,509
Change related to credit allowance	45		(79)
Other changes in the period	(8,972)		6,456
Balance at end of period	10,167		18,622
Contract Liabilities
Balance at beginning of period	226,237	166,918	166,918
Change due to acquisitions / disposals	1,610		39,885
Other changes in the period	20,550		19,434
Balance at end of period	248,397		$ 226,237
Revenue related to our contract liabilities	$ 167,800
Calculated under Revenue Guidance in Effect before Topic 606 [Member]
Contract Liabilities
Revenue related to our contract liabilities		$ 126,800