Summary of Significant Accounting Policies - Acquisition Related Expenses and Other One-Time Transaction Related Expenses (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Merger related costs:
Strategic advisory services	$ 35,765	$ 62,332	$ 0
Transfer taxes	5,109	8,931	0
Legal fees and expenses	5,464	15,081	2,603
Personnel costs and other reimbursements	751	3,612	0
Multi-tenant spin-off	7,450	0	0
Other fees and expenses	1,676	8,450	0
Other non-routine costs:
Post-transaction support services	14,251	4,000
Subordinated distribution fee	78,244	98,360	0
Audit Committee Investigation and related litigation	17,660	0	0
Furniture, fixtures and equipment	14,085	5,800	0
Legal fees and expenses	8,325	950	0
Personnel costs and other reimbursements	2,718	2,546	0
Other fees and expenses	9,016	481	0
Total	$ 200,514	$ 210,543	$ 2,603