Business Segments (Revenue by Geographic Area) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Revenues from External Customers and Long-Lived Assets [Line Items]
Total segment revenues	$ 251,235	$ 241,552	$ 238,069	$ 232,154	$ 241,026	$ 241,414	$ 239,357	$ 253,980	$ 963,010	$ 975,777	$ 1,041,179
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total segment revenues									812,653	837,049	903,511
Rest of world
Revenues from External Customers and Long-Lived Assets [Line Items]
Total segment revenues									$ 150,357	$ 138,728	$ 137,668