Fair Value Measurements and Derivative Instruments (Recurring) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Assets:
Derivative financial instruments	$ 4,759	$ 0
Liabilities:
Derivative financial instruments	914,477	703,654
Fair Value, Measurements, Recurring | Total Fair Value
Assets:
Derivative financial instruments	134,574	63,981
Investments	3,965	5,531
Total Assets	138,539	69,512
Liabilities:
Derivative financial instruments	1,044,292	767,635
Total Liabilities	1,044,292	767,635
Fair Value, Measurements, Recurring | Level 1
Assets:
Derivative financial instruments	0	0
Investments	3,965	5,531
Total Assets	3,965	5,531
Liabilities:
Derivative financial instruments	0	0
Total Liabilities	0	0
Fair Value, Measurements, Recurring | Level 2
Assets:
Derivative financial instruments	134,574	63,981
Investments	0	0
Total Assets	134,574	63,981
Liabilities:
Derivative financial instruments	1,044,292	767,635
Total Liabilities	1,044,292	767,635
Fair Value, Measurements, Recurring | Level 3
Assets:
Derivative financial instruments	0	0
Investments	0	0
Total Assets	0	0
Liabilities:
Derivative financial instruments	0	0
Total Liabilities	$ 0	$ 0