Accrued Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Payables and Accruals [Abstract]
Accrued employee compensation, benefits and withholdings	$ 48,078	$ 63,742	$ 46,262
Accrued property taxes	43,662	42,510	42,912
Customer deposits and prepayments	39,125	43,574	35,748
Accrued interest and contract adjustment payments	35,149	31,759	30,426
CIAC current portion	1,485	1,485	1,552
Other (none of which is individually significant)	28,573	32,431	37,140
Total accrued liabilities	$ 196,072	$ 215,501	$ 194,040