Fair Value Measurement (Investments in LLCs and Limited Partnerships) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Investments in private funds [Abstract]
Investments in limited liability companies and limited partnerships fair value	$ 162,624	$ 133,250
Private debt funds [Member]
Investments in private funds [Abstract]
Investments in limited liability companies and limited partnerships unfunded commitments	14,267
Investments in limited liability companies and limited partnerships fair value	50,268	37,296
Long equity fund [Member]
Investments in private funds [Abstract]
Investments in limited liability companies and limited partnerships unfunded commitments	0
Investments in limited liability companies and limited partnerships fair value	6,407	6,747
Long/Short equity funds [Member]
Investments in private funds [Abstract]
Investments in limited liability companies and limited partnerships unfunded commitments	0
Investments in limited liability companies and limited partnerships fair value	28,030	25,301
Non-public equity funds [Member]
Investments in private funds [Abstract]
Investments in limited liability companies and limited partnerships unfunded commitments	48,381
Investments in limited liability companies and limited partnerships fair value	65,722	51,811
Multi-strategy fund of funds [Member]
Investments in private funds [Abstract]
Investments in limited liability companies and limited partnerships unfunded commitments	0
Investments in limited liability companies and limited partnerships fair value	8,252	8,271
Structured credit fund [Member]
Investments in private funds [Abstract]
Investments in limited liability companies and limited partnerships unfunded commitments	0
Investments in limited liability companies and limited partnerships fair value	$ 3,945	$ 3,824