Fair Value Measurements Debt at at Carrying and Fair Value (Details) (Discounted cash flow [Member], USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Parent Company [Member] | Carrying Value [Member]
Liabilities:
Long-term Debt, Excluding Current Maturities, Fair Value Disclosure	$ 5,238,042	$ 5,232,476
Parent Company [Member] | Carrying Value [Member] | Level 2 [Member]
Liabilities:
Junior subordinated notes	250,000	250,000
Long-term debt (fixed-rate), net of discount	4,689,042	4,683,476
Long Term Debt (variable rate) net of discount	299,000	299,000
Parent Company [Member] | Fair Value [Member]
Liabilities:
Long-term Debt, Excluding Current Maturities, Fair Value Disclosure	6,614,466	6,162,680
Parent Company [Member] | Fair Value [Member] | Level 2 [Member]
Liabilities:
Junior subordinated notes	296,696	269,366
Long-term debt (fixed-rate), net of discount	6,018,770	5,594,314
Long Term Debt (variable rate) net of discount	299,000	299,000
Subsidiaries [Member] | Carrying Value [Member]
Liabilities:
Long-term Debt, Excluding Current Maturities, Fair Value Disclosure	3,763,258	3,763,258
Subsidiaries [Member] | Carrying Value [Member] | Level 2 [Member]
Liabilities:
Junior subordinated notes	250,000	250,000
Long-term debt (fixed-rate), net of discount	3,513,258	3,513,258
Subsidiaries [Member] | Fair Value [Member]
Liabilities:
Long-term Debt, Excluding Current Maturities, Fair Value Disclosure	4,649,286	4,307,821
Subsidiaries [Member] | Fair Value [Member] | Level 2 [Member]
Liabilities:
Junior subordinated notes	296,696	269,366
Long-term debt (fixed-rate), net of discount	$ 4,352,590	$ 4,038,455