Fair Value of Assets and Liabilities - Debt Fair Value (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Jun. 17, 2020	Dec. 31, 2019
Senior Unsecured Notes, due 2021 at 4.25%
Fair Value of Assets and Liabilities
Interest rate, stated percentage	4.25%		4.25%
Senior Unsecured Notes, due 2022 at 5.00%
Fair Value of Assets and Liabilities
Interest rate, stated percentage	5.00%		5.00%
Senior Unsecured Notes, due 2023 at 4.50%
Fair Value of Assets and Liabilities
Interest rate, stated percentage	4.50%		4.50%
Senior Unsecured Notes, due 2024 at 4.65%
Fair Value of Assets and Liabilities
Interest rate, stated percentage	4.65%		4.65%
Senior Unsecured Notes, due 2024 at 4.35%
Fair Value of Assets and Liabilities
Interest rate, stated percentage	4.35%		4.35%
Senior Unsecured Notes, due 2025 at 4.50%
Fair Value of Assets and Liabilities
Interest rate, stated percentage	4.50%		4.50%
Senior Unsecured Notes, due 2025 at 7.50%
Fair Value of Assets and Liabilities
Interest rate, stated percentage	7.50%	7.50%	7.50%
Senior Unsecured Notes, due 2026 at 5.25%
Fair Value of Assets and Liabilities
Interest rate, stated percentage	5.25%		5.25%
Senior Unsecured Notes, due 2026 at 4.75%
Fair Value of Assets and Liabilities
Interest rate, stated percentage	4.75%		4.75%
Senior Unsecured Notes, due 2027 at 4.95%
Fair Value of Assets and Liabilities
Interest rate, stated percentage	4.95%		4.95%
Senior Unsecured Notes, due 2028 at 3.95%
Fair Value of Assets and Liabilities
Interest rate, stated percentage	3.95%		3.95%
Senior Unsecured Notes, due 2029 at 4.95%
Fair Value of Assets and Liabilities
Interest rate, stated percentage	4.95%		4.95%
Senior Unsecured Notes, due 2030 at 4.375%
Fair Value of Assets and Liabilities
Interest rate, stated percentage	4.375%		4.375%
Carrying Value
Fair Value of Assets and Liabilities
Total financial liabilities	$ 5,732,018		$ 5,287,658
Carrying Value | Senior Unsecured Notes, due 2021 at 4.25%
Fair Value of Assets and Liabilities
Total financial liabilities	49,887		398,379
Carrying Value | Senior Unsecured Notes, due 2022 at 5.00%
Fair Value of Assets and Liabilities
Total financial liabilities	497,427		496,821
Carrying Value | Senior Unsecured Notes, due 2023 at 4.50%
Fair Value of Assets and Liabilities
Total financial liabilities	499,514		499,432
Carrying Value | Senior Unsecured Notes, due 2024 at 4.65%
Fair Value of Assets and Liabilities
Total financial liabilities	348,497		348,295
Carrying Value | Senior Unsecured Notes, due 2024 at 4.35%
Fair Value of Assets and Liabilities
Total financial liabilities	818,810		818,075
Carrying Value | Senior Unsecured Notes, due 2025 at 4.50%
Fair Value of Assets and Liabilities
Total financial liabilities	346,774		346,431
Carrying Value | Senior Unsecured Notes, due 2025 at 7.50%
Fair Value of Assets and Liabilities
Total financial liabilities	788,098		0
Carrying Value | Senior Unsecured Notes, due 2026 at 5.25%
Fair Value of Assets and Liabilities
Total financial liabilities	343,649		343,083
Carrying Value | Senior Unsecured Notes, due 2026 at 4.75%
Fair Value of Assets and Liabilities
Total financial liabilities	446,210		445,905
Carrying Value | Senior Unsecured Notes, due 2027 at 4.95%
Fair Value of Assets and Liabilities
Total financial liabilities	395,027		394,649
Carrying Value | Senior Unsecured Notes, due 2028 at 3.95%
Fair Value of Assets and Liabilities
Total financial liabilities	391,333		390,759
Carrying Value | Senior Unsecured Notes, due 2029 at 4.95%
Fair Value of Assets and Liabilities
Total financial liabilities	417,703		417,307
Carrying Value | Senior Unsecured Notes, due 2030 at 4.375%
Fair Value of Assets and Liabilities
Total financial liabilities	389,089		388,522
Fair Value
Fair Value of Assets and Liabilities
Total financial liabilities	5,342,603		5,499,211
Fair Value | Senior Unsecured Notes, due 2021 at 4.25%
Fair Value of Assets and Liabilities
Total financial liabilities	49,925		406,838
Fair Value | Senior Unsecured Notes, due 2022 at 5.00%
Fair Value of Assets and Liabilities
Total financial liabilities	490,115		526,500
Fair Value | Senior Unsecured Notes, due 2023 at 4.50%
Fair Value of Assets and Liabilities
Total financial liabilities	480,255		520,478
Fair Value | Senior Unsecured Notes, due 2024 at 4.65%
Fair Value of Assets and Liabilities
Total financial liabilities	317,597		364,277
Fair Value | Senior Unsecured Notes, due 2024 at 4.35%
Fair Value of Assets and Liabilities
Total financial liabilities	748,584		848,847
Fair Value | Senior Unsecured Notes, due 2025 at 4.50%
Fair Value of Assets and Liabilities
Total financial liabilities	318,931		361,783
Fair Value | Senior Unsecured Notes, due 2025 at 7.50%
Fair Value of Assets and Liabilities
Total financial liabilities	847,704		0
Fair Value | Senior Unsecured Notes, due 2026 at 5.25%
Fair Value of Assets and Liabilities
Total financial liabilities	319,519		369,185
Fair Value | Senior Unsecured Notes, due 2026 at 4.75%
Fair Value of Assets and Liabilities
Total financial liabilities	402,597		464,315
Fair Value | Senior Unsecured Notes, due 2027 at 4.95%
Fair Value of Assets and Liabilities
Total financial liabilities	351,598		414,012
Fair Value | Senior Unsecured Notes, due 2028 at 3.95%
Fair Value of Assets and Liabilities
Total financial liabilities	326,966		393,940
Fair Value | Senior Unsecured Notes, due 2029 at 4.95%
Fair Value of Assets and Liabilities
Total financial liabilities	360,906		434,248
Fair Value | Senior Unsecured Notes, due 2030 at 4.375%
Fair Value of Assets and Liabilities
Total financial liabilities	$ 327,906		$ 394,788