Organization and Basis of Presentation - Accumulated Other Comprehensive Loss Summary (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2017 USD ($)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at period beginning	$ 6,292,237
Balance at period end	6,383,894
Accumulated Other Comprehensive Loss, Net [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at period beginning	(32,098)
Other comprehensive income before reclassification	15,414
Amounts reclassified from accumulated other comprehensive loss	(7,948)
Other comprehensive income	7,466
Balance at period end	(24,632)
Change in Fair Value and Amortization of Swap Settlements [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at period beginning	(32,963)
Other comprehensive income before reclassification	13,512
Amounts reclassified from accumulated other comprehensive loss	(6,352)
Other comprehensive income	7,160
Balance at period end	(25,803)
Unrealized Gains/(Loss) on Available for Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at period beginning	865
Other comprehensive income before reclassification	1,902
Amounts reclassified from accumulated other comprehensive loss	(1,596)
Other comprehensive income	306
Balance at period end	$ 1,171