Leases (ROU Assets and Lease Liabilities) (Detail) - USD ($) $ in Thousands		Mar. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Operating lease right-of-use assets		$ 109,448	$ 110,000	$ 0
Finance lease ROU asset accumulated amortization		43,300
Total leased right-of-use assets		124,988
Current portion: Operating lease liabilities		23,820		0
Noncurrent portion: Operating lease liabilities		91,380		$ 0
Noncurrent portion: Finance lease liabilities		7,301
Total lease liabilities		128,998
Property And Equipment [Member]
Finance lease right-of-use assets	[1]	15,540
Current Portion Of Long-Term Debt And Finance Lease Obligations [Member]
Current portion: Finance lease liabilities		$ 6,497

[1] Finance lease right-of-use assets are presented net of accumulated amortization of $43.3 million as of March 31, 2019.