Fair Value of Assets and Liabilities - Debt Fair Value (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Senior Unsecured Notes, due 2022 at 5.00%
Fair Value of Assets and Liabilities
Interest rate, stated percentage	5.00%
Senior Unsecured Notes, due 2023 at 4.50%
Fair Value of Assets and Liabilities
Interest rate, stated percentage	4.50%
Senior Unsecured Notes, due 2024 at 4.65%
Fair Value of Assets and Liabilities
Interest rate, stated percentage	4.65%
Senior Unsecured Notes, due 2024 at 4.35%
Fair Value of Assets and Liabilities
Interest rate, stated percentage	4.35%
Senior Unsecured Notes, due 2025 at 4.50%
Fair Value of Assets and Liabilities
Interest rate, stated percentage	4.50%
Senior Unsecured Notes, due 2025 at 7.50%
Fair Value of Assets and Liabilities
Interest rate, stated percentage	7.50%
Senior Unsecured Notes, due 2026 at 5.25%
Fair Value of Assets and Liabilities
Interest rate, stated percentage	5.25%
Senior Unsecured Notes, due 2026 at 4.75%
Fair Value of Assets and Liabilities
Interest rate, stated percentage	4.75%
Senior Unsecured Notes, due 2027 at 4.95%
Fair Value of Assets and Liabilities
Interest rate, stated percentage	4.95%
Senior Unsecured Notes, due 2027 at 5.50%
Fair Value of Assets and Liabilities
Interest rate, stated percentage	5.50%
Senior Unsecured Notes, due 2028 at 3.95%
Fair Value of Assets and Liabilities
Interest rate, stated percentage	3.95%
Senior Unsecured Notes, due 2029 at 4.95%
Fair Value of Assets and Liabilities
Interest rate, stated percentage	4.95%
Senior Unsecured Notes, due 2030 at 4.375%
Fair Value of Assets and Liabilities
Interest rate, stated percentage	4.375%
Carrying Value
Fair Value of Assets and Liabilities
Total financial liabilities	$ 6,133,376	$ 6,130,166
Carrying Value | Senior Unsecured Notes, due 2022 at 5.00%
Fair Value of Assets and Liabilities
Total financial liabilities	498,335	498,032
Carrying Value | Senior Unsecured Notes, due 2023 at 4.50%
Fair Value of Assets and Liabilities
Total financial liabilities	499,637	499,596
Carrying Value | Senior Unsecured Notes, due 2024 at 4.65%
Fair Value of Assets and Liabilities
Total financial liabilities	348,801	348,700
Carrying Value | Senior Unsecured Notes, due 2024 at 4.35%
Fair Value of Assets and Liabilities
Total financial liabilities	819,913	819,546
Carrying Value | Senior Unsecured Notes, due 2025 at 4.50%
Fair Value of Assets and Liabilities
Total financial liabilities	347,290	347,118
Carrying Value | Senior Unsecured Notes, due 2025 at 7.50%
Fair Value of Assets and Liabilities
Total financial liabilities	789,590	789,006
Carrying Value | Senior Unsecured Notes, due 2026 at 5.25%
Fair Value of Assets and Liabilities
Total financial liabilities	344,495	344,212
Carrying Value | Senior Unsecured Notes, due 2026 at 4.75%
Fair Value of Assets and Liabilities
Total financial liabilities	446,668	446,515
Carrying Value | Senior Unsecured Notes, due 2027 at 4.95%
Fair Value of Assets and Liabilities
Total financial liabilities	395,594	395,405
Carrying Value | Senior Unsecured Notes, due 2027 at 5.50%
Fair Value of Assets and Liabilities
Total financial liabilities	442,620	442,370
Carrying Value | Senior Unsecured Notes, due 2028 at 3.95%
Fair Value of Assets and Liabilities
Total financial liabilities	392,195	391,908
Carrying Value | Senior Unsecured Notes, due 2029 at 4.95%
Fair Value of Assets and Liabilities
Total financial liabilities	418,300	418,102
Carrying Value | Senior Unsecured Notes, due 2030 at 4.375%
Fair Value of Assets and Liabilities
Total financial liabilities	389,938	389,656
Fair Value
Fair Value of Assets and Liabilities
Total financial liabilities	6,242,078	6,361,902
Fair Value | Senior Unsecured Notes, due 2022 at 5.00%
Fair Value of Assets and Liabilities
Total financial liabilities	509,578	510,285
Fair Value | Senior Unsecured Notes, due 2023 at 4.50%
Fair Value of Assets and Liabilities
Total financial liabilities	509,858	505,280
Fair Value | Senior Unsecured Notes, due 2024 at 4.65%
Fair Value of Assets and Liabilities
Total financial liabilities	350,432	347,893
Fair Value | Senior Unsecured Notes, due 2024 at 4.35%
Fair Value of Assets and Liabilities
Total financial liabilities	821,985	819,328
Fair Value | Senior Unsecured Notes, due 2025 at 4.50%
Fair Value of Assets and Liabilities
Total financial liabilities	345,725	346,462
Fair Value | Senior Unsecured Notes, due 2025 at 7.50%
Fair Value of Assets and Liabilities
Total financial liabilities	910,616	926,404
Fair Value | Senior Unsecured Notes, due 2026 at 5.25%
Fair Value of Assets and Liabilities
Total financial liabilities	354,715	354,996
Fair Value | Senior Unsecured Notes, due 2026 at 4.75%
Fair Value of Assets and Liabilities
Total financial liabilities	426,434	448,506
Fair Value | Senior Unsecured Notes, due 2027 at 4.95%
Fair Value of Assets and Liabilities
Total financial liabilities	395,262	404,328
Fair Value | Senior Unsecured Notes, due 2027 at 5.50%
Fair Value of Assets and Liabilities
Total financial liabilities	474,766	491,918
Fair Value | Senior Unsecured Notes, due 2028 at 3.95%
Fair Value of Assets and Liabilities
Total financial liabilities	367,578	388,146
Fair Value | Senior Unsecured Notes, due 2029 at 4.95%
Fair Value of Assets and Liabilities
Total financial liabilities	408,179	430,064
Fair Value | Senior Unsecured Notes, due 2030 at 4.375%
Fair Value of Assets and Liabilities
Total financial liabilities	$ 366,950	$ 388,292