Other Financial Statement Disclosures - Long Term Debt (Details) - USD ($)	Jun. 30, 2016	Apr. 30, 2016	Mar. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Total carrying value	$ 2,645,367,000			$ 2,692,419,000
Senior Notes [Member] | 5% Senior Notes, due September 2017 [Member]
Debt Instrument [Line Items]
Total carrying value	$ 356,953,000			$ 365,494,000
Stated rate	5.00%	5.00%	5.00%	5.00%
Principal amount	$ 357,700,000.0			$ 366,600,000.0
Effective rate	5.20%			5.20%
Senior Notes [Member] | 7.875% Senior Notes, due August 2019 [Member]
Debt Instrument [Line Items]
Total carrying value	$ 394,492,000			$ 432,870,000
Stated rate	7.875%	7.875%	7.875%	7.875%
Principal amount	$ 396,500,000.0			$ 435,500,000.0
Effective rate	8.00%			8.00%
Senior Notes [Member] | 4.875% Senior Notes, due June 2022 [Member]
Debt Instrument [Line Items]
Total carrying value	$ 705,753,000			$ 706,236,000
Stated rate	4.875%			4.875%
Principal amount	$ 700,000,000			$ 700,000,000
Effective rate	4.70%			4.70%
Senior Notes [Member] | 4.75% Senior Notes, due January 2024 [Member]
Debt Instrument [Line Items]
Total carrying value	$ 397,250,000			$ 397,069,000
Stated rate	4.75%			4.75%
Principal amount	$ 400,000,000			$ 400,000,000
Effective rate	4.80%			4.80%
Senior Notes [Member] | 5.4% Senior Notes due, December 2042 [Member]
Debt Instrument [Line Items]
Total carrying value	$ 394,818,000			$ 394,720,000
Stated rate	5.40%			5.40%
Principal amount	$ 400,000,000			$ 400,000,000
Effective rate	5.40%			5.40%
Senior Notes [Member] | 5.85% Senior Notes, due January 2044 [Member]
Debt Instrument [Line Items]
Total carrying value	$ 396,101,000			$ 396,030,000
Stated rate	5.85%			5.85%
Principal amount	$ 400,000,000			$ 400,000,000
Effective rate	5.90%			5.90%