Fair Value Measurements and Derivative Instruments (Nonrecurring) (Details) - Fair Value, Measurements, Nonrecurring - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Level 1
Assets:
Cash and cash equivalents	$ 287,852,000	$ 120,112,000
Total Assets	287,852,000	120,112,000
Liabilities:
Long-term debt (including current portion of long-term debt)	0	0
Total Liabilities	0	0
Level 2
Assets:
Cash and cash equivalents	0	0
Total Assets	0	0
Liabilities:
Long-term debt (including current portion of long-term debt)	10,244,214,000	8,038,092,000
Total Liabilities	10,244,214,000	8,038,092,000
Level 3
Assets:
Cash and cash equivalents	0	0
Total Assets	0	0
Liabilities:
Long-term debt (including current portion of long-term debt)	0	0
Total Liabilities	0	0
Total Carrying Amount
Assets:
Cash and cash equivalents	287,852,000	120,112,000
Total Assets	287,852,000	120,112,000
Liabilities:
Long-term debt (including current portion of long-term debt)	9,871,267,000	7,506,312,000
Total Liabilities	9,871,267,000	7,506,312,000
Equity-method investment - SkySea Holding	0
Total Fair Value
Assets:
Cash and cash equivalents	287,852,000	120,112,000
Total Assets	287,852,000	120,112,000
Liabilities:
Long-term debt (including current portion of long-term debt)	10,244,214,000	8,038,092,000
Total Liabilities	$ 10,244,214,000	$ 8,038,092,000