Fair Value of Financial Instruments (Fair Value Measurements for Level 3 Instruments) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance	$ 169,314	$ 0
Total realized and unrealized gains (losses):
Included in net income	548	0
Included in other comprehensive income	0	0
Purchases, sales, issuances and settlements, net	(34,946)	0
Transfers into (out of) Level 3	0	0
Balance at end of period	134,916	0
Amount of total gains (losses) for the period included in net income attributable to the change in unrealized gains (losses) relating to assets still held at the end of period	0	0
Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance	193,338	2,718
Total realized and unrealized gains (losses):
Included in net income	2,651	1,481
Included in comprehensive income	0	0
Purchases, sales, issuances and settlements, net	(35,453)	(126)
Transfers into (out of) Level 3	0	0
Balance at end of period	160,536	4,073
Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss)	2,085	1,551
Debt Securities, Available for Sale [Member]
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance	0	0
Total realized and unrealized gains (losses):
Included in net income	0	0
Included in other comprehensive income	0	0
Purchases, sales, issuances and settlements, net	0	0
Transfers into (out of) Level 3	0	0
Balance at end of period	0	0
Amount of total gains (losses) for the period included in net income attributable to the change in unrealized gains (losses) relating to assets still held at the end of period	0	0
Equity Securities, Available for Sale [Member]
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance	0	0
Total realized and unrealized gains (losses):
Included in net income	0	0
Included in other comprehensive income	0	0
Purchases, sales, issuances and settlements, net	0	0
Transfers into (out of) Level 3	0	0
Balance at end of period	0	0
Amount of total gains (losses) for the period included in net income attributable to the change in unrealized gains (losses) relating to assets still held at the end of period	0	0
Derivatives, Index Options [Member]
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance	169,314	0
Total realized and unrealized gains (losses):
Included in net income	548	0
Included in other comprehensive income	0	0
Purchases, sales, issuances and settlements, net	(34,946)	0
Transfers into (out of) Level 3	0	0
Balance at end of period	134,916	0
Amount of total gains (losses) for the period included in net income attributable to the change in unrealized gains (losses) relating to assets still held at the end of period	$ 0	$ 0