Long-Term Debt (Details) $ in Thousands, € in Millions	Dec. 31, 2017 USD ($)	Dec. 31, 2017 EUR (€)	Dec. 31, 2016 USD ($)
Long-Term Debt
Debt, Long-term and short-term, excluding financing costs	$ 7,706,604		$ 9,574,650
Less: unamortized debt issuance costs	(167,153)		(187,214)
Total debt, net of unamortized debt issuance costs	7,539,451		9,387,436
Less: current portion	(1,188,514)		(1,285,735)
Long-term portion	6,350,937		8,101,701
$1.4 billion unsecured revolving credit facility, LIBOR plus 1.175%, currently 2.64% and a facility fee of 0.20%, due 2020
Long-Term Debt
Long-term debt	300,000		925,000
$1.2 billion unsecured revolving credit facility, LIBOR plus 1.175%, currently 2.58% and a facility fee of 0.20%, due 2022
Long-Term Debt
Long-term debt	280,000		805,000
Unsecured senior notes and senior debentures, 2.65% to 7.50%, due 2018, 2020, 2022, 2027 and 2028
Long-Term Debt
Long-term debt	1,866,359		1,073,261
$200 million unsecured term loan, LIBOR plus 1.30%
Long-Term Debt
Long-term debt	0		200,000
$841.8 million unsecured term loan, LIBOR plus 1.00%, currently 2.52% due through 2028
Long-Term Debt
Long-term debt	736,604		806,756
$226.1 million unsecured term loan, 2.53%, due through 2028
Long-Term Debt
Long-term debt	197,837		216,677
€700.7 million unsecured term loan, EURIBOR plus 1.15% currently 1.15%, due through 2028
Long-Term Debt
Long-term debt	736,020		708,417
$742.1 million unsecured term loan, LIBOR plus 1.30%, currently 2.81%, due through 2027
Long-Term Debt
Long-term debt	587,497		649,338
$273.2 million unsecured term loan, LIBOR plus 1.75%
Long-Term Debt
Long-term debt	0		273,166
$519 million unsecured term loan, LIBOR plus 0.45%, currently 2.00%, due through 2020
Long-Term Debt
Long-term debt	129,786		173,049
$420 million unsecured term loan, 5.41%, due through 2021
Long-Term Debt
Long-term debt	135,514		171,444
$420 million unsecured term loan, LIBOR plus 1.65%, currently 3.21%, due through 2021
Long-Term Debt
Long-term debt	140,000		175,000
€159.4 million unsecured term loan, EURIBOR plus 1.58%, currently 1.58%, due through 2021
Long-Term Debt
Long-term debt	63,798		70,082
$524.5 million unsecured term loan, LIBOR plus 0.50%, currently 1.96%, due through 2021
Long-Term Debt
Long-term debt	174,833		218,542
$566.1 million unsecured term loan, LIBOR plus 0.37%, currently 1.90%, due through 2022
Long-Term Debt
Long-term debt	212,276		259,448
$1.1 billion unsecured term loan, LIBOR plus 1.65%, currently 3.21%, due through 2022
Long-Term Debt
Long-term debt	345,877		460,652
$632.0 million unsecured term loan, LIBOR plus 0.40%, currently 1.86%, due through 2023
Long-Term Debt
Long-term debt	315,979		368,643
$673.5 million unsecured term loan, LIBOR plus 0.40%, currently 1.92%, due through 2024
Long-Term Debt
Long-term debt	392,860		448,983
$65.0 million unsecured term loan, LIBOR plus 1.45%, currently 3.02%, due through 2019
Long-Term Debt
Long-term debt	65,227		67,027
$380.0 million unsecured term loan, LIBOR plus 1.45%, currently 3.02%, due 2018
Long-Term Debt
Long-term debt	380,000		380,000
$791.1 million unsecured term loan, LIBOR plus 1.30%, currently 2.85%, due through 2026
Long-Term Debt
Long-term debt	593,331		659,256
$290.0 million unsecured term loan, LIBOR plus 1.75%
Long-Term Debt
Long-term debt	0		290,000
€365 million unsecured term loan, EURIBOR plus 1.75%
Long-Term Debt
Long-term debt	0		123,963
$7.3 million unsecured term loan, LIBOR plus 2.5%
Long-Term Debt
Long-term debt	0		3,964
$30.3 million unsecured term loan, LIBOR plus 3.75%, currently 5.29%, due through 2021
Long-Term Debt
Long-term debt	5,400		6,597
€80.0 million unsecured term loan, EURIBOR plus 1.32% currently 1.32%, due through 2024
Long-Term Debt
Long-term debt	14,267	€ 11.9	0
Capital lease obligations
Long-Term Debt
Capital lease obligations	$ 33,139		$ 40,385