Leases (Summary of Lease Assets and Liabilities) (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Leases [Abstract]
Operating lease asset	$ 154,676	$ 170,056
Finance lease asset	13,728	15,713
Total lease assets	168,404	185,769
Operating lease liability, current	29,780	30,171
Finance lease liability, current	3,399	3,788
Total lease liabilities, current	33,179	33,959
Operating lease liability, noncurrent	185,201	193,570
Finance lease liability, noncurrent	29,133	17,477
Total lease liabilities, noncurrent	214,334	211,047
Total lease liabilities	$ 247,513	$ 245,006