Leases (Summary of Lease Assets and Liabilities) (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Leases [Abstract]
Operating lease asset	$ 172,575	$ 0
Finance lease asset	16,085
Total lease assets	188,660
Operating lease liability, current	29,519
Finance lease liability, current	3,830
Total lease liabilities, current	33,349
Operating lease liability, noncurrent	197,006
Finance lease liability, noncurrent	18,245
Total lease liabilities, noncurrent	215,251
Total lease liabilities	$ 248,600